From Digital to Analogue Magnetoelectronics Theory of Transport in Non-Collinear Magnetic N

Designation:A773/A773M–01Standard Test Method fordc Magnetic Properties of Materials Using Ring and Permeameter Procedures with dc Electronic Hysteresigraphs1This standard is issued under thefixed designation A773/A773M;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1This test method provides dc hysteresigraph procedures (B-H loop methods)for the determination of basic magnetic properties of materials in the form of ring,toroidal,link, double-lapped Epstein cores,or other standard shapes that may be cut,stamped,machined,or ground from cast,compacted, sintered,forged,or rolled materials.It includes tests for normal induction and hysteresis taken under conditions of continuous sweep magnetization.Rate of sweep may be varied,either manually or automatically at different portions of the curves during tracing.Total elapsed time for tracing a hysteresis loop is commonly10to120s per loop.1.2The values and equations stated in customary(cgs-emu and inch-pound)or SI units are to be regarded separately as standard.Within th is standard,SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore,each system shall be used independently of the other. Combining values from the two systems may result in noncon-formance with this standard.1.3This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1ASTM Standards:2A34/A34M Practice for Sampling and Procurement Test-ing of Magnetic MaterialsA341/A341M Test Method for Direct Current Magnetic Properties of Materials Using D-C Permeameters and the Ballistic Test MethodsA343/A343M Test Method for Alternating-Current Mag-netic Properties of Materials at Power Frequencies Using Wattmeter-Ammeter-V oltmeter Method and25-cm Epstein Test FrameA596/A596M Test Method for Direct-Current Magnetic Properties of Materials Using the Ballistic Method and Ring Specimens2.2Other:IEC Publication404-4:Magnetic Materials—Part4:Meth-ods of Measurement of dc Magnetic Properties of Iron and Steel(1995)33.Summary of Test Method3.1As in making most magnetic measurements,a specimen is wound with an exciting winding(the primary)and a search coil(the secondary)for measuring the change influx.When an exciting current,I,is applied to the primary winding,a magneticfield,H,is produced in the coil,and this in turn produces magneticflux f in the specimen.In uniform speci-mens that do not contain air gaps,such as ring samples,all of the exciting current is used to magnetize the specimen,and H is proportional to I in accordance with the following equation:H5KI(1) where:H=magneticfield strength,Oe[A/m];I=current in the exciting coil A;andK=constant determined by the number of primary turns the magnetic path length of the specimen and systemof units.3.1.1The magneticflux may be determined by integration of the instantaneous electromotive force that is induced in the secondary coil when theflux is increased or decreased by a varying H.The instantaneous voltage,e,is equal to:e52NK1d fdt(2)or1This test method is under the jurisdiction of ASTM Committee A06on Magnetic Properties and is the direct responsibility of Subcommittee A06.01on Test Methods.Current edition approved June10,2001.Published September2001.Originally approved st previous edition approved in1996as A773–96.2For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at service@.For Annual Book of ASTMStandards volume information,refer to the standard’s Document Summary page on the ASTM website.3Available from American National Standards Institute,25W.43rd St.,4th Floor,New York,NY10036.1Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.f 51K 1N*edtwhere:dt =time differential,N =number of turns,andK 1=10−8for cgs-emu system,or K 1=1for SI system.The flux f can be obtained if *edt can be determined.This can be accomplished by several means,as described in ASTM STP 526.(1)4The most common method uses an electronic integrator consisting of a high-gain dc amplifier with resistive-capacitive feedback.The relationship to *edt is:E 51RC*edt(3)where:E =output voltage,V ;R =input resistance of the integrator in the secondarycircuit,V ;andC =the feedback capacitance,F .By combining the two equations:f 5ERC K 1N or E 5f NK 1RC(4)If the voltage,E ,is applied to the Y axis of an X-Y recorder,the Y deflection of the pen is proportional to the flux,f .3.1.2Measurements of magnetic field strength and flux by the hysteresigraph method is illustrated in the block diagram of Fig.1.The system consists of a magnetizing power source,an exciting current controller,an electronic flux integrator,and a data recorder.As exciting current is applied to the coil,a voltage proportional to I is produced across the shunt resistor which is connected in series with the primary coil.This voltage determines the value of H .3.1.3In the testing of hard magnetic materials,or soft magnetic materials in the form of wire,bars or rods,it is usually necessary to use a permeameter.This is shown in theblock diagram of Fig.2.When using permeameters,the value of H in the gap is generally not proportional to I that flows through the exciting coil of the yoke.In these cases,the value of H is determined by integration of the electromotive force that is induced in an H coil (or Chattock potentiometer)or from the signal developed by a Hall probe which is placed near the specimen.When using an H coil,the determination of H is accomplished with an H integrator in exactly the same manner as that used to determine flux with the B integrator described in 3.1.When using a Hall sensor,the H values are determined from the voltage output which is proportional to H .In some cases,the H versus I relationship may be sufficiently linear from 0to the coercive field strength (H c )of the material under test.In such cases,it is acceptable to determine the second quadrant of the hysteresis loop by determining H from the value of I in the exciting winding.4.Significance and Use4.1Hysteresigraph testing permits more rapid and efficient collection of dc hysteresis (B-H loop)data as compared to the point by point ballistic Test Methods A 341/A 341M and A 596/A 596M .The accuracy and precision of testing is comparable to the ballistic methods.Hysteresigraphs are par-ticularly desirable for testing of semihard and hard magnetic materials where either the entire second quadrant (demagneti-zation curve)or entire hysteresis loop is of primary concern.4.2Provided the test specimen is representative of the bulk sample or lot,this test method is well suited for design,specification acceptance,service evaluation and research and development.5.Interferences5.1Test methods using suitable ring-type specimens are the preferred methods for determining the basic magnetic proper-ties of a material.However,this test method has several important requirements.Unless adequate inside diameter to outside diameter ratios are maintained in the test specimens,the magnetic field strength will be excessively nonuniform throughout the test material and the measured parameters cannot be represented as material properties.The basic quality4The boldface numbers in parentheses refer to the list of references at the end of this testmethod.FIG.1Block Diagram of Ring TestApparatus2of materials having directional sensitive properties cannot be tested satisfactorily with punched rings or laminations.With them it is necessary to use Epstein specimens cut with their lengths in the direction of specific interest or use long link-shaped or spirally wound core test specimens whose long dimensions are similarly oriented.The acceptable minimum width of strip used in such test specimens is also sensitive to the material under test.At present,it is believed the silicon steels should have a strip width of at least 3cm [30mm].Unless ring specimens are large,it is difficult to provide sufficient magnetizing turns or current-carrying capacity to reach high magnetic field strengths.In general,magnetic materials tend to have nonuniform properties throughout the body of the test specimens;for this reason,uniformly distrib-uted test windings and uniform specimen cross-sectional area are highly desirable to average nonuniform behavior to a tolerable degree.5.2When conducting permeameter tests on bars,rods,and other appropriate specimens,this test method covers a range of magnetic field strengths from about 0.05Oe [4A/m]up to about 20000Oe [1600kA/m]or more,depending on the specimen geometry and the particular permeameter that is used.In general,the lower limit of magnetic field strength is determined by the area-turns of the H coil (or the sensitivity of the Hall probe if it is used),the sensitivity of the integrator,and the sensitivities of the measuring and recording components.The upper limitation in magnetic field strength is determined by the type of permeameter appropriate for the specimen,the power supply,and the heat generated in the yoke windings.Recommendations of the useful range of magnetic field strength for the various permeameters are shown in Table 1.Other types may be used with appropriate precautions.5.2.1In general,permeameters do not maintain a uniform magnetic field in either the axial or radial directions around the test specimen.The field gradients in both of these directionswill differ in the various permeameters.Also the H -sensing and B -sensing coils of the different permeameters are not identical in area,in turns,or in length or identically located.Although test specimens are prepared to have uniform physical cross section,they may have undetected nonuniform magnetic prop-erties radially or axially along the specimen length adjacent to the H or B coils.Some permeameters may also introduce clamping strains into the test specimen.For these reasons test results obtained on a test specimen with one type of permeame-ter may not compare closely with those obtained on the same specimen from another type permeameter,and both may differ from more precise testing methods.5.2.2The limitation in the B measurement by this test method is determined by the number of turns on the specimen,the cross-sectional area,the permeability,and the sensitivities of the B integrator and X-Y recorder.In general,normal induction and hysteresis data may be determined from a flux linkage corresponding to 1000Maxwell turns [10−5Weber turns]to an upper induction that corresponds to the intrinsic saturation for mostmaterials.FIG.2Block Diagram of Permeator Test ApparatusTABLE 1Permeameters Recommended for Use WithHysteresigraphsN OTE —Other permeameters may be suitable for use with dc hysteresi-graphs where appropriate modifications are made.Refer to Test Method A 341/A 341M for other permeameters.PermeameterMagnetic Field Strength RangeH MeasurementDevice OekA/m Babbit (2,3)40/100 3.2/8current,H coil Fahy Simplex (4,5,6)0.1/3000.008/24H coil Fahy Simplex Super H Adapter (6)100/25008/200H coilIEC Type A 12/25001/200H coil,Hall probe IEC Type B 12/6201/50H coilIsthmus (6,7)100/20000+8/1600+H coil,Hall probe35.2.3Some permeameters use compensation coils and re-quire continual adjustment of the currentflowing through these coils.This may not be compatible with commercially available hysteresigraphs and can be a source of significant error.5.2.4The magnetic test results,particularly for high perme-ability alloys,may not exactly agree with test results obtained by the ballistic methods,Test Methods A341/A341M and A596/A596M.This is due to the influence of eddy currents and the different nature of the magnetizing waveform between hysteresigraph and ballistic testing.6.Apparatus6.1The apparatus shall consist of as many of the compo-nents described in6.2-6.6as required to perform the tests. 6.1.1All apparatus used in this test method shall be cali-brated against known standards to ensure the accuracy limits given below.6.2Balance or Scales:6.2.1The balance or scales used to weigh the test specimen shall be capable of weighing to an accuracy of0.2%.6.2.2The micrometer or dimensional measuring scales used to determine specimen dimensions for calculation of cross-sectional area shall be capable of measuring to an accuracy of at least0.1%.6.3Magnetizing Power Source—The power source may range from simple batteries to sophisticated regulated,low-ripple,protected,programmable types.It shall have sufficient capacity to produce the maximum currents required for mag-netization of the specimen under test.6.4Exciting Current Controller—Instantaneous value of magnetizing current,and its rate of change,may be controlled entirely manually by means of rheostats,potentiometers, shunts,reversing switches,and so forth;semiautomatically by means of variable-speed motors or sweep generators,and so forth;or entirely automatic by means of rate sensors,and so forth.In all cases,components shall be capable of carrying the required currents without overheating,and controls shall be of such design that magnetizing current may be increased or decreased in a uniform manner so that smooth traces are plotted on the X-Y recorder.6.5B or H Integrator—Theflux integrator(s)may be any of the types described in ASTM STP526(or other)and should have sufficient sensitivity,stability,linearity,and freedom from drift to ensure an accuracy of at least0.5%of full scale. 6.6Data Recorder—The B and H values can be recorded and displayed by either analog or digital X-Y chart recorders, dataloggers,or computers.The recording device shall be capable of resolving B or H values of1%of the full-scale value.For analog to digital converters,twelve-bit resolution is desirable.7.Test Specimens for Ring-Type Measurements7.1The specifications in7.2-7.8cover the general case for specimens in which magneticfield strength is proportional to the exciting current,that is,H=kI.7.2When the test specimen represents a test lot of material, its selection shall conform to the requirements of Practice A34/A34M or of an individual specification.7.3To qualify as a test specimen suitable for evaluation of material properties,the effective ratio of mean diameter to radial width shall be not less than10to1(or an inside diameter to outside diameter ratio not less than0.82).When the test specimen has smaller ratios than the above requirements,the test data should not be represented as material properties but should be called core properties because of nonuniformflux distribution.7.4When link,oval-shaped,or rectangular test specimen forms are used,the requirements of7.3apply to the end or corner sections whereflux crowding occurs.When straight-sided test specimens are very long relative to the length of the corner or end sections,they are suitable for basic material properties evaluation with relatively unoriented materials, provided the uncertainty in determination of true-path(effec-tive)length is less than1%of the total path length.When this uncertainty in path length(shortest or longest relative to the mean-path length)exceeds1%,the test values should be reported as core properties and not basic material properties.7.5The test specimen may be constructed of solid,lami-nated,or strip materials and in any of the shapes described in 1.1.7.6Test specimen cores made from strip may be laminated, machined,spirally wound,or Epstein specimens(the method of selection for Epstein specimens is described in Annex A3of Test Method A343).When the material is to be tested half transverse and half longitudinal,the material shall be cut into Epstein strips or square laminations of adequate dimensional ratio.7.7Test specimens used for basic material evaluation shall be cut,machined,ground,slit,or otherwise formed to have a cross section that remains sufficiently uniform that its nonuni-formity will not materially affect the accuracy of establishing and measuring induction,B,or magneticfield strength,H,in the test specimen.7.8When required for material properties development,the test specimen shall have received a stress relief or other anneal after preparation.This anneal is subject to agreement between manufacturer and purchaser.8.Test Specimens for Permeameter Measurements8.1The specifications in8.2-8.11cover the general case for specimens in which the magnetizing force is not proportional to exciting current and the specimen must be tested in conjunction with a suitable permeameter.8.2Where possible,test specimen cross-sectional area shall be directly measured using calipers or micrometers.If not possible because of cross-sectional shape or surface roughness, then the cross-sectional area shall be determined from the mass,length,and assumed density of the test specimen.8.3Test specimens in bar form may be of round,square,or rectangular cross-sectional shape.In some permeameters,the bar specimen may be a half round or any shape having a uniform cross-sectional area.Permeameters must have a good magnetic joint between the ends of the test specimen and the permeameter yoke or pole faces.Generally,to achieve a good magnetic joint,the test specimen must be of square or rectangular cross section and must be machined or groundto 4have straight and parallel surfaces.For permeameters using specimens butted to the pole tips,the specimen ends must be smooth and parallel.8.4When the material is in flat-rolled form and is to be evaluated as half transverse-half longitudinal,the test sample shall be sheared to have strip specimens in multiples of four in accordance with Table 2.When flat-rolled material is to be evaluated in only one direction,the test specimen shall conform to Table 2or to the requirements for best test quality for the particular permeameter being used.For flat-rolled materials of thickness 0.0100in.[0.254mm]or thinner,the test specimen cross-sectional area shall be not less than 0.310in.2[200mm 2]and not more than 0.620in.2[400mm 2].8.5When the test specimen for strip materials is to be half transverse and half longitudinal,the strips shall be positioned to be composed of alternately transverse and longitudinal throughout the specimen and a transverse strip shall be placed adjacent to the permeameters yoke or pole face.8.6For full testing accuracy,the length and size of the test specimen must meet the requirements of the permeameter being used.Generally for most permeameters,a test specimen length of 10in.[254mm]or more is required.Shorter specimens with some permeameters require the use of pole-piece extensions and may cause a reduction in testing accuracy.Other permeameters are designed for short specimens without loss of testing accuracy.8.7When the test specimen is short and is to butt endwise directly against the pole piece or pole piece extensions,it shall have ends with flat,smooth,and parallel surfaces.8.8All test specimen forms shall be cut,machined,or ground to have a uniform cross-sectional area along the active length of the test specimen.The cross-sectional area shall be sufficiently uniform so that its nonuniformity does not materi-ally affect the accuracy of establishing and measuring induc-tion in the test specimen.8.9When required for development of material properties,the test specimen shall receive a stress relief or other anneal after preparation.This anneal is subject to agreement between manufacturer and purchaser.8.10Specimens of permanent-magnet material shall be processed previous to testing in accordance with a procedure acceptable to both the manufacturer and the purchaser.8.11The test specimen shall conform to the requirements of Practice A 34/A 34M .9.Calibration of Integrator(s)9.1The integrator(s)may be calibrated by any convenient means that will ensure an integration accuracy of at least 0.5%.Calibration may be accomplished by means of a certified Maxwell-turns generator,or volt-seconds generator,ormutual inductor,or by verification of input resistors and feed-back capacitors in operational amplifier-type integrators.10.Calibration of Magnetizing Circuit10.1In cases in which the magnetic field strength is proportional to current,such as in ring specimens,long solenoids,special permeameters,and so forth,the shunt resistor(s)through which the magnetizing current flows shall be verified to at least 0.1%,at rated current.11.Calibration of Data Recorder11.1The various scales of the data recorder shall be calibrated by means of a verified voltage source to at least the quoted accuracy of the recorder in use.12.Procedure12.1The following test procedure is based on a hysteresi-graph which features both manual and automatic control of magnetizing current,operational amplifier-type integrators,and an analog X-Y recorder.The use of other hysteresigraphs,including fully computerized units,is permissible and detailed operating steps will vary.However,the general test procedure is similar in all units.The following procedure covers manual current sweeping,automatic current sweeping,and automatic current sweeping with symmetrical tracing.12.2Setup —The procedures of 12.2.1-12.2.6should be observed for all methods of current sweep.12.2.1Before beginning a test,allow a minimum warmup period of 10min for all apparatus and instrumentation.12.2.2Connect the specimen,observing polarity so that the pen of the recorder moves in the first quadrant on initial application of exciting current.(It is imperative that proper polarity be established before demagnetization of the test specimen.)12.2.3Before test,demagnetize the specimen through the coils by ac or dc techniques by establishing a magnetic field strength sufficiently large to reach a point well above the knee of the magnetization curve.Then,while continuously cycling the magnetization,slowly reduce the magnetizing current to zero.(In the demagnetization process,down-switching of voltage taps to reduce current may result in current surges.It is advisable to select voltage sources and controls that have the ability to reduce current to a low value without switching taps,preferably to a current level that does not exceed a value of 0.1times the coercivity of the material.)12.2.4For the B measurement,set the B integrator range and scaling potentiometer so that B is read directly on the Y axis of the recorder.12.2.5For the H measurement,select the appropriate shunt resistor (current range)and set the scaling potentiometer so that H is read directly on the X axis.12.2.6Before starting the current sweep,adjust the drift in the integrators to minimum.12.3Manual Sweep Method —If a specimen is completely demagnetized,it is possible to obtain a normal induction curve and symmetrical hysteresis loop by using manual sweep methods.However,since it is difficult to obtain smooth traces by manual control,recording by manual sweep is recom-mended only when the test specimens have relatively lowTABLE 2Number of Test StripNominal Thickness Electrical Sheet Gage Number Number of Stripsin.mm 0.0100to 0.02500.254to 0.63532to 24120.0280to 0.04350.711to 1.10523to1980.0500and over1.270and over18and thicker45permeabilities,large cross sections,and a large number of secondary turns.(This permits coarser B and H calibrations, and sweep control is not so crucial.)12.3.1Before testing,follow the setup procedure described in12.2.1-12.2.6.12.3.2The controller shall be used in the manual mode.The sweep current is controlled manually by the H-sweep control.12.3.3With the origin at the center of the X-Y coordinates and with the recorder pen in the down position,set the H sweep control at zero(center tap of control).Trace the normal induction curve by turning the control until the pen reaches the desired+H m on the recorder.At+H m turn the control to decrease the magneticfield strength until the pen traverses to point B r(center tap of control)where the current reverses. Continue to turn the control,increasing the current negatively, until the pen reaches points−H c and−H m.Then turn to+H m to complete the loop tracing.Minor loops are obtainable at any point of the major loop by reversing the control in incremental amounts.12.3.4If the loop obtained in12.3.3is symmetrical about the origin,the trace from the origin to H m is similar to a normal induction curve;any point on the major loop is valid and may be read directly.However,if the loop is significantly displaced as a result of incomplete demagnetization,the initial curve is not a valid normal induction curve.If the major loop is only moderately displaced,approximate values for points(H m,B m), H c,and B r may be obtained by averaging corresponding positive and negative values.12.3.5In obtaining magnetization and hysteresis data by hysteresigraph methods,very often the H c value of the speci-men is very small relative to H m so that H c and B r cannot be resolved with high accuracy.However,this is overcome by expanding the H scale(increasing the H sensitivity)when the pen reaches B r(or H=0).When recording manually,stop the current sweep at+B r then change the current range setting (shunts)to give the appropriate sensitivity to measure H c accurately(ratios to2.5to300are possible).An alternative method is simply to change the x sensitivity on the recorder when the pen reaches+B r.If extreme changes in sensitivity are required,a combination of both methods may be used. 12.3.6In obtaining a major hysteresis loop,a minimum of two loops shall be traced to assure that the specimen is in a symmetrically cyclically magnetized state and to assure that significant drift has not occurred during the test.12.4Automatic Sweep Method—In obtaining magnetization and hysteresis data by hysteresigraph methods,automatic sweeps are preferable because of better control of sweep current for tracing smooth loops.If a specimen is completely demagnetized,it is possible to obtain curves similar to normal induction curves and symmetrical hysteresis loops.12.4.1Before testing,follow the setup procedure described in12.2.1-12.2.6.12.4.2Switch the controller to the automatic mode.This introduces the controller circuitry for automatic control of the sweep current.12.4.3Select the appropriate current range(shunts)and set the H-scaling control to give the desired full-scale magnetic field strength.12.4.4Set the control,H control,to give the desired peak magneticfield strength.(The H m(%))helipot may be varied to give any whole or fractional part of the full-scale magnetic field strength).12.4.5Set the sweep speed of the controller to20s or longer per loop,adjust the drift to a minimum,and place the pen of the recorder in the down position at the origin.12.4.6Begin the current sweep.If the specimen is com-pletely demagnetized,a normal induction curve will be traced in thefirst quadrant to(+H m,B m),then H is automatically reduced and the trace proceeds to(0,+B r).The current sweep is automatically switched in polarity,and the second and third quadrants are traced.At(−H m,−B m)the current sweep is again reduced,and the remaining half of the hysteresis loop is traced. It is advisable to trace at least two complete loops to ascertain if significant drift has occurred during the plot.12.4.7If the loop traced in12.4.6is symmetrical about the origin,the trace from the origin to H m is similar to a normal induction curve;any point on the major loop is valid and may be read directly.If the loop is significantly displaced because of incomplete demagnetization,the initial curve is not valid.If the major loop is only moderately displaced,approximate values for points B r,H c,(H m,B m)or any other may be obtained by averaging corresponding positive and negative values.12.4.8If the H c values of the specimen is very small relative to H m so that H c and B r cannot be resolved with high accuracy, the H scale may be expanded to give increased sensitivities for accurate reading of B r and H c.Follow the procedures as described in12.3.5.12.4.9Minor hysteresis loops are obtainable at any point of the major loop by reversing the current sweep in incremental amounts.12.5Automatic Sweep With Symmetrical Trace Method—The preferred method for obtaining magnetization and hyster-esis data by hysteresigraph methods is to use symmetrical trace circuitry which enables automatic tracing of symmetrical hysteresis loops about the origin.By this method,a loop is traced symmetrically about the origin regardless of the degree of residual magnetism in the specimen.In using the automatic symmetrical method of hysteresigraph testing,a normal induc-tion curve is determined(point by point)from the positive tips of major hysteresis loops.The curve is obtained by tracing a number of symmetrical loops,starting at low values of H and progressively increasing the size of the loops in convenient steps.Plots of the various loop tips will give the normal induction curve.For greater sensitivity and maximum use of chart area,the automatic symmetrical mode may be used to advantage by tracing half loops by placing the origin at a convenient location in the lower left hand section of the chart and recording only the positive tips of the hysteresis loops in thefirst quadrant.In this case,the pen is over driven in the X and Y directions,but this does not alter the accuracy.12.5.1Before testing a specimen,follow the setup proce-dure described in12.2.1to12.2.6.The use of symmetrical tracing does not eliminate the need for demagnetization when maximum inductions less than those corresponding to the knee of the magnetization curve are to bemeasured. 6。

Third Edition (© 2001 McGraw-Hill) Chapter 88.1 Inductance of a long solenoid Consider the very long (ideally infinitely long) solenoid shown in Figure 8.69. If r is the radius of the core and is the length of the solenoid, then >> r. The total number of turns is N and the number of turns per unit length is n = N/ . The current through the coil wires is I. Apply Ampere's law around C, which is the rectangular circuit PQRS,and show thatB≈μoμr nIFurther, show that the inductance isL≈μoμr n2V core Inductance of long solenoid where V core is the volume of the core. How would you increase the inductance of a long solenoid?Figure 8.69What is the approximate inductance of an air-cored solenoid with a diameter of 1 cm, length of 20 cm, and 500 turns? What is the magnetic field inside the solenoid and the energy stored in the whole solenoid when the current is 1 A? What happens to these values if the core medium has a relative permeability μr of 600? SolutionWe use Ampere's law in Equation 8.15. Consider Figure 8.9. If H is the field along a small length d along a closed path C, then around C, ⎰Hd= total threaded current = I total = NI.Figure 8.9:Ampere’s circuital lawAssume that the solenoid is infinitely long. The rectangular loop PQRS has n (PQ ) number of turns where n is the number of turns per unit length or n = N / (See Figure 8.69). The field is only inside the solenoid and only along the PQ direction (long solenoid assumption) and therefore the field along QR , RS and SP is zero. Assume that the field H is uniform across the solenoid core cross section. Then the path integral of the magnetic field intensity H around PQRS is simply is H = H (PQ ). Ampere's law ⎰ Hd = I total is then H (PQ ) = I (nPQ ) i.e.H = nIThe dimensions of the solenoid are such that length >> diameter. We can assume that H field isrelatively uniform at all points inside the solenoid. Note: The approximate equality sign in the text (equation for B ) is due to the fact that we assumed H is uniform across the core and, further, along the whole length of the solenoid from one end to the other. The ends of the solenoid will have different fields (lower). Let A be the cross-sectional area of the solenoid. The magnetic field B , the flux Φ and hence the inductance L are B = μo μr H ≈ μo μr nI∴ Φ = BA ≈ μo μr nAI = μo μr (N / )AIand L = (N Φ)/I = N [μo μr (N / )AI ]/I = μo μr (N 2/ )A = μo μr n 2( A ) ∴L = μo μr n 2V corewhere V core is the volume of the core. Inductance depends on n 2, where n is the number of turns per unit length, on the relative permeability μr and on the volume of the core containing the magnetic flux. For a given volume inductor, L can be increased by using a higher μr material or increasing n , e.g. thinner wire to get more turns per unit length (not so thin that the skin effect diminishes the Q -factor, quality factor; see §2.8). The theoretical inductance of the coil is L = (4π ⨯ 10-7 H/m)(1)[(500)/(0.2 m)]2(0.2 m)(π)[(0.01 m)/(2)]2 ∴ L = 1.23 ⨯ 10-4 H or 0.123 mHB ≈ (4π ⨯ 10-7 Wb A -1 m -1)(1)[(500)/(0.2 m)](1 A) = 3.14 ⨯ 10-3 T The energy per unit volume is,E vol = B 2/(2μo ) = (3.14 ⨯ 10-3 T)2/[2(4π ⨯ 10-7 Wb A -1 m -1)] ∴E vol = 3.92 J / m 3The total energy stored is then,()()()J 61.6tot μm 2.02m 01.0J/m 92.3Area Length 23vol =⎪⎭⎫ ⎝⎛=⨯=πE E Suppose that μr = 600 and suppose that the core does not saturate (an ideal ferromagnetic material) then, ()()H 0.0738=⨯≈-600H 1023.14L()()T 1.88=⨯≈-600T 1014.33Band()()()372vol J/m 2344600m Wb/A 1042T 88.1=⋅⨯≈-πEso that E tot = (E vol )(Volume) = 36.8 mJThis is a dramatic increase and shows the virtue of using a magnetic core material for increasing theinductance and the stored magnetic energy.8.2 Magnetization Consider a long solenoid with a core that is an iron alloy (see Problem 8.1 for therelevant formulas). Suppose that the diameter of the solenoid is 2 cm and the length of the solenoid is 20 cm. The number of turns on the solenoid is 200. The current is increased until the core is magnetized to saturation at about I = 2 A and the saturated magnetic field is 1.5 T.a . What is the magnetic field intensity at the center of the solenoid and the applied magnetic field, μo H , forsaturation? b . What is the saturation magnetization M sat of this iron alloy?c . What is the total magnetization current on the surface of the magnetized iron alloy specimen?d . If we were to remove the iron-alloy core and attempt to obtain the same magnetic field of 1.5 T inside thesolenoid, how much current would we need? Is there a practical way of doing this?Solutiona. Applying Ampere’s law or H = NI we have,()()m2.0A 2200==NI H Since I = 2 A gives saturation, corresponding magnetizing field is H sat ≈ 2000 A/mSuppose the applied magnetic field is the magnetic field in the toroid core in the absence of material. ThenB ap p =μo H sat =4π⨯10-7 Wb A -1 m -1()2000 A/m () ∴ B app = 2.51 ⨯ 10-3 Tb. Apply()sat sat sat H M B o +=μ∴ A/m 2000mA Wb 104T5.11-1-7sat satsat -⨯=-=-πμH B M o∴ M sat ≈ 1.19 ⨯ 106 A/m c. Since M is the magnetization current per unit length,I m = M sat ≈ 1.19 ⨯ 106 A/mThen I surf ace = Total circulating surface current:∴I surface =I m =1.19⨯106 A/m ()0.2 m ()=2.38⨯105 ANote that the actual current in the wires, 2 A is negligible compared with I surf ace . d. Apply, B ≈μo nI (for air)()⎪⎭⎫⎝⎛⨯≈-m 2.0200m A Wb 104T5.11-1-7πI = 1194 ANot very practical in every day life! Perhaps this current (thus field B = 1.5 T) could be achieved byusing a superconducting solenoid.8.3 Paramagnetic and diamagnetic materials Consider bismuth with χm = -16.6×10-5 andaluminum with χm = 2.3×10-5. Suppose that we subject each sample to an applied magnetic field B o of 1 T applied in the +x direction. What is the magnetization M and the equivalent magnetic field μo M in each sample? Which is paramagnetic and which is diamagnetic?SolutionBismuth: χm = -16.6×10-5 χm is negative and small. Bismuth is a diamagnetic material.M = χm H = χm B o /μo∴M = (-16.6×10-5) (1 Wb m -2)/(4π×10-7 Wb m -1 A -1) = -132.1 A m -1Negative sign indicate – x direction.Magnetic field = B o + μo M = B o + χm B o = B o (1 + χm ) = (1 - 16.6×10-5)(1 T) = 0.999834 TAluminum: χm = 2.3×10-5 χm is positive and small. Aluminum is paramagnetic material.M = χm H = χm B o /μo∴M = (2.3×10-5) (1 Wb m -2)/(4π×10-7 Wb m -1 A -1) = 18.3 A m -1Positive sign indicates + x direction.Magnetic field = B o + μo M = B o + χm B o = B o (1 + χm ) = (1 +2.3×10-5)(1 T) = 1.000023 T Author's Note: Both effects are quite small.8.4 Mass and molar susceptibilities Sometimes magnetic susceptibilities are reported as molar ormass susceptibilities. Mass susceptibility (in m 3 kg -1) is χm /ρ where ρ is the density. Molar susceptibility (inm 3 mol -1) is χm (M at /ρ) where M at is the atomic mass. Terbium (Tb) has a magnetic molar susceptibility of 2 cm 3 mol -1. Tb has a density of 8.2 g cm -3 and an atomic mass of 158.93 g mol -1. What is its susceptibility, masssusceptibility and relative permeability? What is the magnetization in the sample in an applied magnetic field of 2 T?Solutionχm = Molar susceptibility (ρ/M at ) = (2 cm 3 mol -1) (8.2 g cm -3)/(158.93 g mol -1) = 0.1032 μr = 1 + χm = 1 + 0.1032 = 1. 1032 M = χm H = χm B o /μo∴M = (0.1032)(2 Wb m -2)/(4π×10-7 Wb m -1 A -1) = 1.642×105 A m -1Note: The magnetic field in the sample iso r o r B H B μμμ===1.1032( 2 T) = 2.206 T.8.5 Pauli spin paramagnetism Paramagnetism in metals depends on the number of conductionelectrons that can flip their spins and align with the applied magnetic field. These electrons are near the Fermilevel E F , and their number is determined by the density of states g (E F ) at E F . Since each electron has a spin magnetic moment of β, paramagnetic susceptibility can be shown to be given byχpara ≈ μo β 2 g (E F )Pauli spin paramagnetismwhere the density of states is given by Equation 4.10. The Fermi energy of calcium, E F , is 4.68 eV. Evaluate the paramagnetic susceptibility of calcium and compare with the experimental value of 1.9 ⨯ 10-5.SolutionApply,()()E h m E e 23228⎪⎭⎫⎝⎛=πg(Equation 4.10)so that ()()()()()J/eV 10602.1eV 68.4s J 10626.6kg 10109.928192323431---⨯⎪⎪⎭⎫⎝⎛⋅⨯⨯=πF E g∴g E F ()=9.197⨯1046 J -1 m -3Then, χpara ≈ μo β 2 g (E F )()()()314622241-1-7para m J 10199.9m A 10273.9m A Wb 104----⨯⨯⨯≈πχ∴χpara ≈ 0.994 ⨯ 10-5This is in reasonable agreement within an order of magnitude with the experimental value of 1.9 ⨯ 10-5.8.6 Ferromagnetism and the exchange interaction Consider dysprosium (Dy), which is arare earth metal with a density of 8.54 g cm -3 and atomic mass of 162.50 g mol -1. The isolated atom has theelectron structure [Xe] 4f 106s 2. What is the spin magnetic moment in the isolated atom in terms of number of Bohr magnetons? If the saturation magnetization of Dy near absolute zero of temperature is 2.4 MA m -1, whatis the effective number of spins per atom in the ferromagnetic state? How does this compare with the number of spins in the isolated atom? What is the order of magnitude for the exchange interaction in eV per atom in Dy if the Curie temperature is 85 K?SolutionIn an isolated Dy atom, the valence shells will fill in accordance with the exchange interaction:4f 106s 2Obviously, there are 4 unpaired electrons. Therefore for an isolated Dy atom, the spin magnetic moment = 4β.Atomic concentration in dysprosium (Dy) solid is (where ρ is the density, N A is Avogadro’s number and M at is the atomic mass):()()3283-12333m 10165.3kg/mol1050.162mol 10022.6kg/m 1054.8--⨯=⨯⨯⨯==atAat M N n ρSuppose that each atom contributes x Bohr magnetons, then βx n M at =sat()()2243286sat mA 10273.9m 10165.3A/m104.2--⨯⨯⨯==βat n M x = 8.18 This is almost twice the net magnetic moment in the isolated atom. Suppose that the Dy atom in the solid loses all the 4 electrons that are paired into the "electron gas" in the solid. This would make Dy +4 have 8 unpaired electrons and a net spin magnetic moment of 8β (this is an oversimplified view).Exchange interaction ~ kT C =8.617⨯10-5 eV/K ()85 K ()=0.00732 eV The order of magnitude of exchange interaction ~ 10-2 eV/atom for Dy (small).8.7 Magnetic domain wall energy and thickness The energy of a Bloch wall depends on twomain factors: the exchange energy E ex (J /atom) and magnetocrystalline energy K (J m -3). If a is the interatomicdistance, δ is the wall thickness, then it can be shown that the potential energy per unit area of the wall isδδπK a E U +=2ex2wall Potential energy of a Bloch wallShow that the minimum energy occurs when the wall has the thickness2/1ex 22⎪⎪⎭⎫ ⎝⎛='aK E πδBloch wall thicknessand show that when δ = δ', the exchange and anisotropy energy contributions are equal . Using reasonable values for various parameters, estimate the Bloch energy and wall thickness for Ni. (See Example 8.4)SolutionδδπK a E U +=2ex2wall∴K a E d dU +-=2ex2wall 2δπδ Minimum energy occurs, when 0wall=δd dU ∴ 022ex 2=+'-K a E δπ ∴2/1ex 22⎪⎪⎭⎫ ⎝⎛='aK E πδAt δδ'=δδδδπ'=''='=K K a E U 2ex 2exchange 2Andexchange anisotropy U K U ='=δFor Ni, T C = 631 K and K = 5 mJ cm -3 = 5×103 J m -3 E ex = kT C = (1.38×10-23 J K -1) (631 K) = 8.71×10-21 J ∴⎥⎦⎤⎢⎣⎡⨯⨯⨯=⎪⎪⎭⎫ ⎝⎛='---)m J 10(5 m)103.0(2)J 1071.8(23392122/1ex 2ππδaK E = 1.69×10-7m or 169 nm And m)10(1.69)m J 105(m)10m)(1.69103.0(2 J) 108.71(27-337-9-212ex 2wall ⨯⨯+⨯⨯⨯='+'=--πδδπK a E U= 1.69×10-3 J m -2 or 1.69 mJ m -2.*8.8 Toroidal inductor and radio engineers toroidal inductance equationa . Consider a toroidal coil (Figure 8.10) whose mean circumference is and has N tightly wound turnsaround it. Suppose that the diameter of the core is 2a and >> a . By applying Ampere's law, show that if the current through the coil is I , then the magnetic field in the core isNIB r o μμ=[8.30]where μr is the relative permeability of the medium. Why do you need >> a for this to be valid? Doesthis equation remain valid if the core cross section is not circular but rectangular, a ⨯ b , and >> a and b ? b . Show that the inductance of the toroidal coil isAN L r o 2μμ=Toroidal coil inductance [8.31]where A is the cross-sectional area of the core.c . Consider a toroidal inductor used in electronics that has a ferrite core size FT-37, that is, round but with arectangular cross section. The outer diameter is 0.375 in (9.52 mm), the inner diameter is 0.187 in (4.75 mm), and the height of the core is 0.125 in (3.175 mm). The initial relative permeability of the ferrite core is 2000, which corresponds to a ferrite called the 77 Mix. If the inductor has 50 turns, then using Equation 8.31, calculate the approximate inductance of the coil. d . Radio engineers use the following equation to calculate the inductances of toroidal coils,6210)mH (N A L L =Radio engineers inductance equation [8.32]where L is the inductance in millihenries (mH) and A L is an inductance parameter, called an inductance index , that characterizes the core of the inductor. A L is supplied by the manufacturers of ferrite cores and is typically quoted as millihenries (mH) per 1000 turns. In using Equation 8.32, one simply substitutes the numerical value of A L to find L in millihenries. For the FT-37 ferrite toroid with the 77 Mix as the ferrite core, A L is specified as 884 mH/1000 turns. What is the inductance of the toroidal inductor in part (c ) from the radio engineers equation in Equation 8.32? What is the percentage difference in values calculated by Equations 8.32 and 8.31? What is your conclusion? (Comment : The agreement is not always this close).SolutionFigure 8.10: A toroidal coil with N turns.a. As in Figure 8.10, if we choose a closed path C that runs along the geometric center of the core and if I is the current, N is the number of turns and = mean circumference, then: NIH d H Ct ==⎰ or H = (NI )/∴NIH B r o r o μμμμ==This particular derivation only applies in the special case of >> radius (a ); that is, for a very long, narrow core. If the core is very long and narrow, it may be safely assumed that the magnetic flux density B is uniform across the entire width (2a ) of the core. If B was not uniform, then applying Ampere’s Law to different (concentric) closed paths would yield different results.This above derivation for B is valid for a rectangular cross-sectioned core of area a ⨯ b , provided that >> a and >> b . The magnetic field is then,B =μo μrNIb. The inductance by definition is given by,A N I NAI N I BA N I N L r o r o 2)(μμμμ=⎪⎭⎫ ⎝⎛==Φ=c.Figure 8Q8-1: Toroidal core with rectangular cross section.Given, outer radius = r outer = 0.00476 m, inner radius = r inner = 0.002375 m and height = H = 0.003175 m.We take the mean circumference through the geometric center of the core so that the mean radius is: mm 5675.32inner innerouter =+-=r r r r ∴()()m 1042.22m 105675.32233--⨯=⨯==ππ rWidth = W = r outer - r inner = 0.002385 mA = Cross sectional area = W ⨯ H = (0.002385 m)(0.003175 m) = 7.572 ⨯ 10-6 m 2. Since >> a and >> b (at least approximately) we can calculate L as follows:AN L r o 2μμ=∴ ()()()()m1042.22m 10572.7502000H/m 10432627---⨯⨯⨯=πL ∴L = 0.00212 H or 2.12 mH (2)d. Using the radio engineer’s equation,()()()mH 2.21mH ===62621050mH 88410N A L L (3)so that 4.07%=⨯-=%100mH21.2mH12.2mH 21.2difference %Equations 2 and 3 differ only by 4.1% in this case. This is a good agreement.*8.9 A toroidal inductora . Equations 8.31 and 8.32 allow the inductance of a toroidal coil in electronics to be calculated. Equation8.32 is the equation that is used in practice. Consider a toroidal inductor used in electronics that has a ferrite core of size FT-23 that is round but with a rectangular cross section. The outer diameter is 0.230 in (5.842 mm), the inner diameter is 0.120 in (3.05 mm), and the height of the core is 0.06 in (1.5 mm). The ferrite core is a 43-Mix that has an initial relative permeability of 850 and a maximum relative permeability of 3000. The inductance index for this 43-Mix ferrite core of size FT-23 is A L =188 (mH/1000 turns). If the inductor has 25 turns, then using Equations 8.31 and 8.32, calculate the inductance of the coil under small-signal conditions and comment on the two values. b . The saturation field, B sat , of the 43-mix ferrite is 0.2750 T. What will be typical dc currents that willsaturate the ferrite core (an estimate calculation is required)? It is not unusual to find such an inductor in an electronic circuit also carrying a dc current? Will your calculation of the inductance remain valid in these circumstances? c . Suppose that the above toroidal inductor discussed in parts (a) and (b) is in the vicinity of a very strongmagnet that saturates the magnetic field inside the ferrite core. What will be the inductance of the coil?Solutiona. Provided that the mean circumference is much greater than any long cross sectional dimension (e.g. >> diameter or >> a and >> b ), then we can use,AN L r o 2μμ≈Note that μr is the initial permeability. We need the mean circumference which can be calculated from the mean radius r ,mm 97.132 that so mm 223.22inner innerouter ===+-=r r r r r π Width = W = r outer - r inner = 0.001396 m and Height = H = 0.0015 m.A = Cross sectional area = W ⨯ HSince >> a and >> b (at least approximately) we can calculate L as follows:)(2WH N L r o μμ≈()()()()()m1097.13m105.1m 10396.125850H/m 10433327----⨯⨯⨯⨯≈πLL ≈ 0.10 mHAnd, the radio engineer’s equation, Equation 8.32, (radio engineers toroidal inductance equation, pg. 6.25 and data pg. 24.7 in The ARRL Handbook 1995)()()mH 0.118===62621025mH 18810N A L L There is a 15% difference between the two inductances; limitations of the approximation are apparent. b. To estimate H sat , we’ll take the maximum relative permeability μr max = 3000 as an estimate in order to findH sat (see Figure 8Q9-1). We know that sat max sat and H B NIH o r μμ==∴satmax sat NI B r o μμ=∴ ()()()m1097.13253000m A Wb 104T 2750.03sat-1-17--⨯⨯=I π∴I sat = 40.8 mAwill saturate the core.Figure 8Q9-1: B versus H curve for 43 - Mix ferrite .If the core is saturated, the calculation of inductance is of course no longer valid as it used the initialpermeability. The inductance now will be much reduced. Since under saturation ∆B = μ0∆H , effectively μr = 1. The use of an initial permeability such as μr = 850 implies that we have small changes (and also reversible changes) near around H = 0 or I = 0.When an inductor carries a dc current in addition to an ac current, the core will operate “centered” at a different part of the material’s B -H curve, depending on the magnitude of the dc current inasmuch as H ∝ I . Thus, a dc current I 1 imposes a constant H 1 and shifts the operation of the inductor to around H 1. μr will depend on the magnitude of the dc current.c. The same effect as passing a large dc current and saturating the core. When the core is saturated, theincrease in the magnetic field B in the core is that due to free space, i.e. ∆B = μo ∆H . This means we can use μ = 1 in Equation 8.31 to find the inductance under saturation. It will be about 0.10 mH / 850 or 0.12 μH , very small.Author’s Note: Static inductance can be defined as L = Flux linked per unit dc current or L = N Φ/I . It applies under dc conditions and I = dc current. For ac signals, the current i will be changing harmonically (or following some other time dependence) and we use the definition⎪⎭⎫ ⎝⎛⎪⎭⎫ ⎝⎛Φ=Φ=dt di dt d N i N L δδ Further, by Faraday’s law, since v is the induced voltage across the inductor by the changing total flux Nd Φ/dt , we can also define L by,⎪⎭⎫ ⎝⎛=dt di L vMoreover, since L = N δΦ/δi we see that the ac L is proportional to the slope of the B versus H behavior.*8.10 The transformera . Consider the transformer shown in Figure 8.70a whose primary is excited by an ac (sinusoidal) voltage offrequency ƒ. The current flowing into the primary coil sets up a magnetic flux in the transformer core. By virtue of Faraday's law of induction and Lenz's law, the flux generated in the core is the flux necessary to induce a voltage nearly equal and opposite to the applied voltage. Thus,dtNAdBdt d ==)linked f lux Total (υwhere A is the cross-sectional area, assumed constant, and N is the number of turns in the primary.Show that if V rms is the rms voltage at the primary (V max = V rms √2) and B m is the maximum magnetic field in the core, thenV rms = 4.44 NAƒB mTransformer equation[8.33]Transformers are typically operated with B m at the "knee" of the B -H curve, which corresponds roughly to maximum permeability. For transformer irons, B m ≈ 1.2 T. Taking V rms = 120 V and a transformer core with A = 10 cm ⨯ 10 cm, what should N be for the primary winding? If the secondary winding is to generate 240 V, what should be the number of turns for the secondary coil?b . The transformer core will exhibit hysteresis and eddy current losses. The hysteresis loss per unitsecond, as power loss in watts, is given byP h = KƒB m n V coreHysteresis loss[8.34]where K = 150.7, ƒ is the ac frequency (Hz), B m is the maximum magnetic field (T) in the core (assumed to be in the range 0.2 - 1.5 T), n = 1.6 and, V core is the volume of the core. The eddy current losses are reduced by laminating the transformer core as shown in Figure 8.70b. The eddy current loss is given bycore 22265.1V d B f P me ⎪⎪⎭⎫⎝⎛=ρEddy current loss [8.35]where d is the thickness of the laminated iron sheet in meters (8.70b) and ρ is its resistivity (Ω m). Suppose that the transformer core has a volume of 0.0108 m 3 (corresponds to a mean circumference of 1.08 m). If the core is laminated into sheets of thickness 1 mm and the resistivity of the transformer iron is 6 ⨯ 10-7 Ω m, calculate both the hysteresis and eddy current losses at f = 60 Hz, and comment on theirrelative magnitudes. How would you achieve this?Figure 8.70(a) A transformer with N turns in the primary. (b) Laminated core reduces eddy current losses.Solutiona. The induced voltage either at the primary or the secondary is given by Faraday’s law of induction (the negative sign indicates an induced voltage opposite to the applied voltage), that is,dtdB NA-=υ Suppose we apply this to the primary winding. Then υ = V m sin(2πft ) where f = 60 Hz and V m is the maximum voltage, that is V m = V rms (√2). ThendtdB NAft V m -=π)2sin( It is clear that B is also a sinusoidal waveform. Integrating this equation we find,)2cos()2(ft f NA V B mππ=which can be written asB = B m cos(2πft )so that the maximum B is B m given byfNAV fNA V B m m ππ222rms==where we used V m = V rms (√2). Thus,V rms =4.44NAfB mLet N P = Primary winding turns and assume f = 60 Hz, then()()()()T 2.1Hz 60m 1.044.4V12044.42rms ==m AfB V P N = 38 turns on primary Secondary winding turns are()()()()T 2.1Hz 60m 1.044.4V2402=S N = 75 turns on secondary b. Part a gives B m = 1.2 T. Then the hysteresis loss isP h =KfB m nV co reB m = 1.2 T()()()()36.1m 0108.0T 2.1Hz 607.150=h P = 131 WEddy current loss iscore 22265.1V d B f P me ⎪⎪⎭⎫ ⎝⎛=ρB m = 1.2 T()()()()W 154=⎪⎪⎭⎫ ⎝⎛Ω⨯=-37222m 0108.0m 106m 001.0T 2.1Hz 6065.1e P With 1 mm lamination and at this low frequency (60 Hz) hysteresis loss seems to dominate the eddycurrent loss. Eddy current loss can be reduced with thinner laminations or higher resistivity core materials (e.g. ferrites at the expense of B max ). Hysteresis loss can be reduced by using different core material but that changes B . Eqn. 8.34 is valid for only silicon steel cores only which have the required typical B m for power applications.8.11 Losses in a magnetic recording head Consider eddy current losses in a permalloymagnetic head for audio recording up to 10 kHz. We will use Equation 8.35 for the eddy current losses.Consider a magnetic head weighing 30 g and made from a permalloy with density 8.8 g cm -3 and resistivity 6 ⨯ 10-7 Ω m. The head is to operate at B m of 0.5 T. If the eddy current losses are not to exceed 1 mW, estimate the thickness of laminations needed. How would you achieve this?SolutionWe will apply the eddy current loss equation in this problem though this equation has a number of assumptions so that answer is only an estimate . The eddy current loss iscore 22265.1V d B f P me ⎪⎪⎭⎫⎝⎛=ρwhere the core volume is3633core m 10409.3 or cm 409.3g/cm8.8g30Density Mass -⨯===V Then,core22265.1V B f P d m e ρ=∴ ()()()()()()362273m10409.3T 5.0Hz 000,1065.1mW 106W 101---⨯⨯⨯=d ∴d = 2.07 μmVery thin (a page of a textbook is typically about 50 - 100 μm).*8.12 Design of a ferrite antenna for an AM receiver We consider an AM radio receiverthat is to operate over the frequency range 530 - 1600 kHz. Suppose that the receiving antenna is to be a coil with a ferrite rod as core, as depicted in Figure 8.71. The coil has N turns, its length is , and the cross-sectional area is A . The inductance, L , of this coil is tuned with a variable capacitor C . The maximum value of C is 265 pF, which with L should correspond to tuning in the lowest frequency at 530 kHz. The coil with the ferrite core receives the EM waves, and the magnetic field of the EM wave permeates the ferrite core and induces a voltage across the coil. This voltage is detected by a sensitive amplifier, and in subsequent electronics it is suitably demodulated. The coil with the ferrite core therefore acts as the antenna of the receiver (ferrite antenna). We will try to find a suitable design for the ferrite coil by carrying out approximate calculations - in practice some trial and error experimentation would also be necessary. We will assume that the inductance of a finite solenoid is2AN L o ri μγμ=Inductance of a solenoid [8.36]where A is the cross-sectional area of the core, is the coil length, N is the number of turns, and γ is a geometric factor that accounts for the solenoid coil being of finite length. Assume γ ≈ 0.75. The resonant frequency f of an LC circuit is given by()2/121LC f π=[8.37]a . If d is the diameter of the enameled wire to be used as the coil winding, then the length ≈ Nd . If we usean enameled wire of diameter 1 mm, what is the number of coil turns, N , we need for a ferrite rod given its diameter is 1 cm and its initial relative permeability is 100? b . Suppose that the magnetic field intensity H of the signal in free space is varying sinusoidally, that isH = H m sin(2πƒt )[8.38]where H m is the maximum magnetic field intensity. H is related to the electric field E at a point by H = E /Z space where Z space is the impedance of free space given by 377 Ω.. Show that the induced voltage at the antenna coil is2ππ377CfdE V m m =Induced voltage across a ferrite antenna [8.39]。

Features _äìÉ`çêÉ∆=_`SNRM »=nck■Single-chip Bluetooth mono headset solution withadvanced echo and noise cancellation ■Low-power consumption: over 7 hours of talk-time from a 120mAh battery ■Built-in high-performance 5th Generation CVC(CVC v5.0) single and dual microphone echo and noise cancellation■Advanced Multipoint support: allows a headset (HFP) connection to 2 phones for voice■Packet Loss Concealment and Bit Error Concealment to improve audio quality in thepresence of air interference■Programmable Audio Prompts■Secure Simple Pairing and Proximity Pairing(headset initiated pairing)■Best-in-class Bluetooth radio with 7.5dBmtransmit power and -91dBm receive sensitivity■64MIPS Kalimba DSP coprocessor■Configurable mono headset software■HFP v1.5 and HSP v1.1 support■Integrated 1.5V and 1.8V linear regulators■Integrated switch-mode regulator■Integrated 150mA lithium battery charger■Integrated high-quality codec with 95dB SNRDAC■68-lead 8 x 8 x 0.9mm, 0.4mm pitch QFN package(pin-for-pin compatible with BlueVox DSP QFN)■Green (RoHS compliant and no antimony orhalogenated flame retardants)■ A complete BC6150 QFN mono headset solutiondevelopment kit, including example design, isavailable. Order code DK‑BC‑6150‑1ABC6150 QFN Mono Headset SolutionFully Qualified Single-chipBluetooth ® v2.1 + EDR SystemProduction InformationBC6150A08Issue 2General Description _`SNRM=nck is a low-cost fully featured ROM chip solution for mono headsets. It features advanced single-microphone and dual-microphone CVC v5.0echo and noise cancellation. BC6150 QFN includes a Bluetooth radio, baseband, Kalimba DSP, DAC /ADC, switch-mode power supply and battery charger in a compact 8 x 8 x 0.9mm QFN package for low-cost designs.Applications■Mono headset solution with advanced echo andnoise cancellationBC6150 QFN also includes state-of-the-art CVC v5.0single and dual-microphone echo and noise reductionincluding significant near end audio enhancements.Dual-microphone CVC v5.0 achieves over 30dBdynamic noise suppression, allowing the headset userto be heard more clearly.BC6150 QFN supports the latest Bluetooth v2.1 + EDRspecification which includes Secure Simple Pairing.This greatly simplifies the pairing process, making iteasier to use a Bluetooth headset.The device incorporates auto-calibration and BISTroutines to simplify development, type approval andproduction test.BC6150 QFN contains the Kalimba DSP coprocessorfor supporting enhanced audio applications.BC6150 QFN is designed to reduce the number ofexternal components required, which minimisesproduction costs._`SNRM=nck Data SheetDocument History RevisionDate Change Reason127 AUG 09Original publication of this document.213 NOV 09Production Information added.SPI interface information updated.If you have any comments about this document, email comments@ givingthe number, title and section with your feedback.Document History_`SNRM=nck Data SheetStatus InformationThe status of this Data Sheet is Production Information .CSR Product Data Sheets progress according to the following format:Advance InformationInformation for designers concerning CSR product in development. All values specified are the target values of thedesign. Minimum and maximum values specified are only given as guidance to the final specification limits and mustnot be considered as the final values.All detailed specifications including pinouts and electrical specifications may be changed by CSR without notice.Pre-production InformationPinout and mechanical dimension specifications finalised. All values specified are the target values of the design.Minimum and maximum values specified are only given as guidance to the final specification limits and must not beconsidered as the final values.All electrical specifications may be changed by CSR without notice.Production InformationFinal Data Sheet including the guaranteed minimum and maximum limits for the electrical specifications.Production Data Sheets supersede all previous document versions.Life Support Policy and Use in Safety-critical ApplicationsCSR's products are not authorised for use in life-support or safety-critical applications. Use in such applications isdone at the sole discretion of the customer. CSR will not warrant the use of its devices in such applications.CSR Green Semiconductor Products and RoHS ComplianceBC6150 QFN devices meet the requirements of Directive 2002/95/EC of the European Parliament and of the Councilon the Restriction of Hazardous Substance (RoHS).BC6150 QFN devices are also free from halogenated or antimony trioxide-based flame retardants and otherhazardous chemicals. For more information, see CSR's Environmental Compliance Statement for CSR GreenSemiconductor Products .Trademarks, Patents and LicencesUnless otherwise stated, words and logos marked with ™ or ® are trademarks registered or owned by CSR plc or itsaffiliates. Bluetooth ® and the Bluetooth ® logos are trademarks owned by Bluetooth ® SIG, Inc. and licensed toCSR. Other products, services and names used in this document may have been trademarked by their respectiveowners.The publication of this information does not imply that any license is granted under any patent or other rights ownedby CSR plc and/or its affiliates.CSR reserves the right to make technical changes to its products as part of its development programme.While every care has been taken to ensure the accuracy of the contents of this document, CSR cannot acceptresponsibility for any errors.Refer to for compliance and conformance to standards information.Status Information_`SNRM=nck Data SheetContents1Device Details (8)2Functional Block Diagram (9)3Package Information (10)3.1Pinout Diagram (10)3.2Device Terminal Functions (11)3.3Package Dimensions (15)3.4PCB Design and Assembly Considerations (16)3.5Typical Solder Reflow Profile (16)4Bluetooth Modem (17)4.1RF Ports (17)4.1.1RF_N and RF_P (17)4.2RF Receiver (17)4.2.1Low Noise Amplifier (17)4.2.2RSSI Analogue to Digital Converter (17)4.3RF Transmitter (18)4.3.1IQ Modulator (18)4.3.2Power Amplifier (18)4.4Bluetooth Radio Synthesiser (18)4.5Baseband (18)4.5.1Burst Mode Controller (18)4.5.2Physical Layer Hardware Engine (18)4.6Basic Rate Modem (18)4.7Enhanced Data Rate Modem (18)5Clock Generation (20)5.1Clock Architecture (20)5.2Input Frequencies and PS Key Settings (20)5.3External Reference Clock (20)5.3.1Input: XTAL_IN (20)5.3.2XTAL_IN Impedance in External Mode (21)5.3.3Clock Start-up Delay (21)5.3.4Clock Timing Accuracy (21)5.4Crystal Oscillator: XTAL_IN and XTAL_OUT (22)5.4.1Load Capacitance (23)5.4.2Frequency Trim (23)5.4.3Transconductance Driver Model (24)5.4.4Negative Resistance Model (24)5.4.5Crystal PS Key Settings (25)6Bluetooth Stack Microcontroller (26)6.1Programmable I/O Ports, PIO and AIO (26)7Kalimba DSP (27)8Memory Interface and Management (28)8.1Memory Management Unit (28)8.2System RAM (28)8.3Kalimba DSP RAM (28)8.4Internal ROM (28)9Serial Interfaces (29)9.1UART Interface (29)9.1.1UART Configuration While Reset is Active (31)9.2Programming and Debug Interface (31)9.2.1Instruction Cycle ..................................................................................................................... 31_`SNRM=nck Data Sheet9.2.2Multi-slave Operation (31)9.3I 2C Interface (31)10Audio Interface (33)10.1Audio Input and Output (33)10.2Mono Audio Codec Interface (33)10.2.1Mono Audio Codec Block Diagram (34)10.2.2ADC (34)10.2.3ADC Digital Gain (34)10.2.4ADC Analogue Gain (35)10.2.5DAC (35)10.2.6DAC Digital Gain (35)10.2.7DAC Analogue Gain (36)10.2.8Microphone Input (36)10.2.9Output Stage (39)10.2.10Side Tone (40)10.2.11Integrated Digital Filter (40)11Power Control and Regulation (42)11.1Power Sequencing (42)11.2External Voltage Source (42)11.3Switch-mode Regulator (43)11.4Low-voltage Linear Regulator (43)11.5Low-voltage Audio Linear Regulator (43)11.6Voltage Regulator Enable Pins (44)11.7Battery Charger (44)11.8LED Drivers (44)11.9Reset, RST# (45)11.9.1Digital Pin States on Reset (46)11.9.2Status after Reset (46)12Example Application Schematic (47)13Electrical Characteristics (48)13.1ESD Precautions (48)13.2Absolute Maximum Ratings (48)13.3Recommended Operating Conditions (48)13.4Input/Output Terminal Characteristics (49)13.4.1Low-voltage Linear Regulator (49)13.4.2Low-voltage Linear Audio Regulator (50)13.4.3Switch-mode Regulator (51)13.4.4Battery Charger (52)13.4.5Reset (53)13.4.6Regulator Enable (53)13.4.7Digital Terminals (54)13.4.8Mono Codec: Analogue to Digital Converter (55)13.4.9Mono Codec: Digital to Analogue Converter (56)13.4.10Clocks (57)13.4.11LED Driver Pads (57)13.4.12Auxiliary ADC (58)14Power Consumption (59)15CSR Green Semiconductor Products and RoHS Compliance (61)15.1RoHS Statement (61)15.1.1List of Restricted Materials (61)16BC6150 QFN Software Stack (62)16.1BC6150 QFN Mono Headset Solution Development Kit (62)16.2BC6150 QFN Mono Headset Solution ................................................................................................. 62_`SNRM=nck Data Sheet16.3Advanced Multipoint Support (62)16.4Programmable Audio Prompts (63)16.5Proximity Pairing (63)16.5.1Proximity Pairing Configuration (63)17Ordering Information (64)17.1BC6150 QFN Mono Headset Solution Development Kit Ordering Information (64)18Tape and Reel Information (65)18.1Tape Orientation (65)18.2Tape Dimensions (65)18.3Reel Information (66)18.4Moisture Sensitivity Level (66)19Document References (67)Terms and Definitions (68)List of FiguresFigure 2.1Functional Block Diagram (9)Figure 3.1Device Pinout (10)Figure 3.2Package Dimensions (15)Figure 4.1Simplified Circuit RF_N and RF_P (17)Figure 4.2BDR and EDR Packet Structure (19)Figure 5.1Clock Architecture (20)Figure 5.2TCXO Clock Accuracy (22)Figure 5.3Crystal Driver Circuit (22)Figure 5.4Crystal Equivalent Circuit (23)Figure 7.1Kalimba DSP Interface to Internal Functions (27)Figure 9.1Universal Asynchronous Receiver (29)Figure 9.2Break Signal (30)Figure 9.3Example EEPROM Connection (32)Figure 10.1BC6150 QFN Audio Interface (33)Figure 10.2Mono Codec Audio Input and Output Stages (34)Figure 10.3ADC Analogue Amplifier Block Diagram (35)Figure 10.4Microphone Biasing (36)Figure 10.5Speaker Output (40)Figure 11.1Voltage Regulator Configuration (42)Figure 11.2LED Equivalent Circuit (45)Figure 12.1Example Application Schematic (47)Figure 16.1Programmable Audio Prompts in External I 2C EEPROM (63)Figure 18.1BC6150 QFN Tape Orientation (65)Figure 18.2Reel Dimensions (66)List of TablesTable 4.1Data Rate Schemes (19)Table 5.1External Clock Specifications (21)Table 5.2Crystal Specification (23)Table 9.1Possible UART Settings (29)Table 9.2Standard Baud Rates (30)Table 9.3Instruction Cycle for a SPI Transaction (31)Table 10.1ADC Digital Gain Rate Selection (34)Table 10.2DAC Digital Gain Rate Selection (35)Table 10.3DAC Analogue Gain Rate Selection (36)Table 10.4Voltage Output Steps ....................................................................................................................... 38_`SNRM=nck Data SheetTable 10.5Current Output Steps (39)Table 11.1BC6150 QFN Voltage Regulator Enable Pins (44)Table 11.2BC6150 QFN Digital Pin States on Reset (46)List of EquationsEquation 5.1Load Capacitance (23)Equation 5.2Trim Capacitance (23)Equation 5.3Frequency Trim (24)Equation 5.4Pullability (24)Equation 5.5Transconductance Required for Oscillation (24)Equation 5.6Equivalent Negative Resistance (25)Equation 9.1Baud Rate (30)Equation 10.1IIR Filter Transfer Function, H(z) (41)Equation 10.2IIR Filter plus DC Blocking Transfer Function, H DC(z) (41)Equation 11.1LED Current (45)Equation 11.2LED PAD Voltage (45)_`SNRM=nckData Sheet1Device DetailsRadio ■Common TX/RX terminal simplifies external matching; eliminates external antenna switch ■BIST minimises production test time ■Bluetooth v2.1 + EDR specification compliant Transmitter ■7.5dBm RF transmit power with level control from a 6-bit DAC over a typical 30dB dynamic range ■Class 2 and Class 3 support without the need for an external power amplifier or TX/RX switch Receiver ■Receiver sensitivity of -91dBm ■Integrated channel filters ■Digital demodulator for improved sensitivity and co-channel rejection ■Real-time digitised RSSI available on HCI interface ■Fast AGC for enhanced dynamic range Synthesiser ■Fully integrated synthesiser requires no external VCO, varactor diode, resonator or loop filter ■Compatible with crystals 16MHz to 26MHz or an external clock 12MHz to 52MHz Kalimba DSP ■Very low power Kalimba DSP coprocessor,64MIPS, 24-bit fixed point core ■Single-cycle MAC; 24 x 24-bit multiply and 56-bit accumulator ■32-bit instruction word, dual 24-bit data memory■6K x 32-bit program RAM, 8K x 24-bit + 8K x 24-bit data RAM ■64 x 32-bit program memory cache when executing from ROM Audio Codec ■16-bit internal codec ■ADC and DAC for stereo audio ■Integrated amplifiers for driving 16Ω speakers; no need for external components ■Support for single-ended speaker termination and line output ■Integrated low-noise microphone bias Physical Interfaces ■Synchronous serial interface for system debugging ■I²C compatible interface to external EEPROMcontaining device configuration data (PS Keys)■UART interface with data rates up to 3Mbits/s■Bidirectional serial programmable audio interfacesupporting PCM, I²S and SPDIF formats■ 2 LED drivers with fadersBaseband and Software■Internal ROM■48KB of internal RAM, allows full-speed datatransfer, mixed voice/data and full piconet support■Logic for forward error correction, header errorcontrol, access code correlation, CRC,demodulation, encryption bit stream generation,whitening and transmit pulse shaping■Transcoders for A-law, µ-law and linear voice fromhost and A-law, µ-law and CVSD voice over air■Configurable mono headset ROM software to set-up headset features and user interface■Support for HFP v1.5 (including three-way calling)and HSP v1.1■Support for Bluetooth v2.1 + EDR specificationSecure Simple Pairing■Proximity Pairing (headset initiated pairing)■Advanced Multipoint support, allowing the headsetto connect to 2 mobile phones or 1 mobile phoneand a VoIP dongle■Programmable audio prompts■Packet Loss Concealment and Bit ErrorConcealment to improve audio quality in thepresence of air interference■DSP based single-microphone CVC v5.0 echo andnoise cancellation is included in the BC6150 QFNfor effective noise cancellation under all conditions■ A high-performance dual-microphone noisecancellation is available using CVC v5.0 is availablein BC6150 QFN providing over 30dB of dynamicnoise suppressionAuxiliary Features■Crystal oscillator with built-in digital trimming■Power management includes digital shutdown andwake-up commands with an integrated low-poweroscillator for ultra-low power Park/Sniff/Hold mode■Clock request output to control external clock■On-chip regulators: 1.5V output from 1.7V to 1.95Vinput■On-chip high-efficiency switched-mode regulator:1.8V output from2.5V to 4.4V input■Power-on-reset cell detects low-supply voltage■10-bit ADC available to applications■On-chip 150mA charger for lithium ion/polymerbatteriesPackage Option■QFN 68-lead, 8 x 8 x 0.9mm, 0.4mm pitch Device Details_`SNRM=nck Data Sheet2Functional Block DiagramG-TW-0115.3.2VREGIN_AUDIO VDD_AUDIO VREGENABLE_L VREGIN_L VREGENABLE_H VSS BAT_PVDD_CHG RF_P XTAL_OUT XTAL_IN LO_REF VDD_LO LED[0]VDD_PADSVDD_MEM RST#TEST_ENVDD_SMP_CORE VDD_CORE VDD_ANA LX VDD_RADIO LED[1]AIO[0]AIO[1]PIO[5:0]VSS_PIO VDD_PIO PIO[14:11, 9]RF_N SPKR_A_PSPKR_A_NMIC_BIASMIC_A_PMIC_A_NMIC_B_NMIC_B_PAU_REF_DCPLUART_TXUART_RXUART_CTS UART_RTS VDD_UARTPIO[7]PIO[8]PIO[6]SPI_CS#SPI_MISO SPI_MOSISPI_CLKFigure 2.1: Functional Block DiagramFunctional Block Diagram_`SNRM=nck Data Sheet3Package Information 3.1Pinout DiagramG-TW-091.4.21234567891018192011121314151617212223242526272829303132333435363738394041424344454647484950515268535455565758596061626364656667Orientation from Top of DeviceFigure 3.1: Device Pinout Package Information_`SNRM=nck Data Sheet3.2Device Terminal FunctionsBluetooth Radio Lead Pad Type Supply Domain DescriptionRF_N65RFVDD_RADIO Transmitter output/switched receiverRF_P64RF Complement of RF_N Synthesiser andOscillatorLead Pad Type Supply Domain DescriptionXTAL_IN3Analogue VDD_ANA For crystal or external clock inputXTAL_OUT4Drive for crystalLO_REF5Reference voltage to decouple the synthesiserSPI Interface Lead Pad Type Supply Domain DescriptionSPI_MOSI28Input, with weak internal pull-downVDD_PADSSPI data inputSPI_CS#30Bidirectional with weakinternal pull-downChip select for SPI, active lowSPI_CLK29Bidirectional with weakinternal pull-downSPI clockSPI_MISO31Bidirectional with weakinternal pull-downSPI data outputUART Interface Lead Pad Type Supply Domain DescriptionUART_TX9Output, tri-state, with weakinternal pull-downVDD_UARTUART data output, active highUART_RX10Bidirectional with weakinternal pull-downUART data input, active highUART_RTS12Bidirectional CMOS output,tri-state, with weak internalpull-upUART request to send active lowUART_CTS11CMOS input with weakinternal pull-downUART clear to send active low_`SNRM=nckData SheetPIO Port Lead Pad Type Supply Domain Description PIO[14]20Bidirectional withprogrammable strength internal pull-up/down VDD_PADS Programmable input/output linePIO[13]19PIO[12]18PIO[11]15PIO[9]14PIO[8]21PIO[7]22PIO[6]23PIO[5]24PIO[4]25PIO[3]58Bidirectional withprogrammable strength internal pull-up/down VDD_PIO Programmable input/output linePIO[2]59PIO[1]60PIO[0]61AIO[1]6Bidirectional VDD_ANA Programmable input/output line AIO[0]7_`SNRM=nck Data SheetAudio Lead Pad Type Supply Domain DescriptionSPKR_A_N56Analogue VDD_AUDIO Speaker output, negative, channel ASPKR_A_P57Analogue VDD_AUDIO Speaker output, positive, channel AMIC_A_N52Analogue VDD_AUDIO Microphone input, negative, channel AMIC_A_P51Analogue VDD_AUDIO Microphone input, positive, channel AMIC_B_N50Analogue VDD_AUDIO Microphone input, negative, channel BMIC_B_P48Analogue VDD_AUDIO Microphone input, positive, channel BMIC_BIAS45Analogue VDD_AUDIO,BAT_PMicrophone biasAU_REF_DCPL55Analogue VDD_AUDIO Decoupling of audio reference, for high-quality audioLED Drivers Lead Pad Type Supply Domain Description LED[1]33Open drain output Open drainLED driver LED[0]32LED driver Test and Debug Lead Pad Type Supply Domain DescriptionRST#26Input with weak internal pull-upVDD_PADSReset if low. Input debounced somust be low for >5ms to cause aresetTEST_EN27Input with strong internal pull-downFor test purposes only, leaveunconnected_`SNRM=nckData SheetPower SuppliesControl Lead DescriptionVREGENABLE_L68Low-voltage linear regulator and low-voltage audiolinear regulator enable, active highVREGIN_L 1Input to internal low-voltage regulatorVREGENABLE_H 35Switch-mode regulator enable, active highVREGIN_AUDIO 46Input to internal audio low-voltage linear regulator VDD_AUDIO 47Positive supply for audioLX 37Switch-mode regulator outputVDD_ANA 2Positive supply output for analogue circuitry and1.5V regulated output, from internal low-voltageregulatorVDD_PIO 62Positive supply for digital input/output ports PIO[3:0]VDD_PADS 16Positive supply for all other digital Input/Output portsincluding PIO[14:11,9:4]VDD_CORE 17, 34Positive supply for internal digital circuitryVDD_RADIO 63, 66Positive supply for RF circuitryVDD_UART 13Positive supply for UART portsVDD_LO 67Positive supply for local oscillator circuitryBAT_P 38Lithium ion/polymer battery positive terminal. Batterycharger output and input to switch-mode regulatorVDD_CHG 39Lithium ion/polymer battery charger inputVDD_SMP_CORE 36Positive supply for switch-mode control circuitry VSS Exposed Pad Ground connectionsUnconnected Leads (N/Cs)Description8, 40, 41, 42, 43, 44, 49, 53, 54Leave unconnected_`SNRM=nck Data Sheet3.3Package DimensionsG-T W-0939.4.3Orientation from TopSeating PlaneOrientation from BottomFigure 3.2: Package Dimensions_`SNRM=nck Data Sheet3.4PCB Design and Assembly ConsiderationsThis section lists recommendations to achieve maximum board-level reliability of the 8 x 8 x 0.9mm QFN 68-leadpackage:■NSMD lands (lands smaller than the solder mask aperture) are preferred, because of the greater accuracy of the metal definition process compared to the solder mask process. With solder mask defined pads, theoverlap of the solder mask on the land creates a step in the solder at the land interface, which can causestress concentration and act as a point for crack initiation.■CSR recommends that the PCB land pattern to be in accordance with IPC standard IPC-7351.■Solder paste must be used during the assembly process.3.5Typical Solder Reflow ProfileSee Typical Solder Reflow Profile for Lead-free Devices for information._`SNRM=nckData Sheet4Bluetooth Modem4.1RF Ports4.1.1RF_N and RF_PRF_N and RF_P form a complementary balanced pair and are available for both transmit and receive. On transmit their outputs are combined using an external balun into the single-ended output required for the antenna. Similarly,on receive their input signals are combined internally.Both terminals present similar complex impedances that may require matching networks between them and the balun. Viewed from the chip, the outputs can each be modelled as an ideal current source in parallel with a lossy capacitor. An equivalent series inductance can represent the package parasitics.G-T W-03349.2.2RF_NRF_PFigure 4.1: Simplified Circuit RF_N and RF_PRF_N and RF_P require an external DC bias. The DC level must be set at VDD_RADIO.4.2RF ReceiverThe receiver features a near-zero IF architecture that allows the channel filters to be integrated onto the die. Sufficient out-of-band blocking specification at the LNA input allows the receiver to be used in close proximity to GSM and W‑CDMA cellular phone transmitters without being desensitised. The use of a digital FSK discriminator means that no discriminator tank is needed and its excellent performance in the presence of noise allows BC6150 QFN to exceed the Bluetooth requirements for co-channel and adjacent channel rejection.For EDR, the demodulator contains an ADC which digitises the IF received signal. This information is then passed to the EDR modem.4.2.1Low Noise AmplifierThe LNA operates in differential mode and takes its input from the shared RF port.4.2.2RSSI Analogue to Digital ConverterThe ADC implements fast AGC. The ADC samples the RSSI voltage on a slot-by-slot basis. The front-end LNA gain is changed according to the measured RSSI value, keeping the first mixer input signal within a limited range. This improves the dynamic range of the receiver, improving performance in interference limited environments._`SNRM=nck Data Sheet4.3RF Transmitter4.3.1IQ ModulatorThe transmitter features a direct IQ modulator to minimise frequency drift during a transmit timeslot, which results in a controlled modulation index. Digital baseband transmit circuitry provides the required spectral shaping.4.3.2Power AmplifierThe internal PA has a maximum output power that allows BC6150 QFN to be used in Class 2 and Class 3 radios without an external RF PA.4.4Bluetooth Radio SynthesiserThe Bluetooth radio synthesiser is fully integrated onto the die with no requirement for an external VCO screening can, varactor tuning diodes, LC resonators or loop filter. The synthesiser is guaranteed to lock in sufficient time across the guaranteed temperature range to meet the Bluetooth v2.1 + EDR specification.4.5Baseband4.5.1Burst Mode ControllerDuring transmission the BMC constructs a packet from header information previously loaded into memory-mapped registers by the software and payload data/voice taken from the appropriate ring buffer in the RAM. During reception, the BMC stores the packet header in memory-mapped registers and the payload data in the appropriate ring buffer in RAM. This architecture minimises the intervention required by the processor during transmission and reception.4.5.2Physical Layer Hardware EngineDedicated logic performs the following:■Forward error correction■Header error control■Cyclic redundancy check■Encryption■Data whitening■Access code correlation■Audio transcodingFirmware performs the following voice data translations and operations:■A-law/µ-law/linear voice data (from host)■A-law/µ-law/CVSD (over the air)■Voice interpolation for lost packets■Rate mismatch correctionThe hardware supports all optional and mandatory features of Bluetooth v2.1 + EDR specification including AFH and eSCO.4.6Basic Rate ModemThe basic rate modem satisfies the basic data rate requirements of the Bluetooth v2.1 + EDR specification. The basic rate was the standard data rate available on the Bluetooth v1.2 specification and below, it is based on GFSK modulation scheme.Including the basic rate modem allows BC6150 QFN compatibility with earlier Bluetooth products.The basic rate modem uses the RF ports, receiver, transmitter and synthesiser, alongside the baseband components described in Section 4.5.4.7Enhanced Data Rate ModemThe EDR modem satisfies the requirements of the Bluetooth v2.1 + EDR specification. EDR has been introduced to provide 2x and 3x data rates with minimal disruption to higher layers of the Bluetooth stack. BC6150 QFN supportsboth the basic and enhanced data rates and is compliant with the Bluetooth v2.1 + EDR specification._`SNRM=nck Data SheetAt the baseband level, EDR uses the same 1.6kHz slot rate and the 1MHz symbol rate defined for the basic data rate. EDR differs in that each symbol in the payload portion of a packet represents 2 or 3 bits. This is achieved using 2 new distinct modulation schemes. Table 4.1 and Figure 4.2 summarise these. Link Establishment and Management are unchanged and still use GFSK for both the header and payload portions of these packets.The enhanced data rate modem uses the RF ports, receiver, transmitter and synthesiser, with the baseband components described in Section 4.5.Data Rate Scheme Bits Per Symbol ModulationBasic Rate 1GFSKEDR 2π/4 DQPSKEDR 38DPSK (optional)Table 4.1: Data Rate SchemesG-TW-0244.2.3Enhanced Data Rate Figure 4.2: BDR and EDR Packet Structure_`SNRM=nck Data Sheet。

As a high school student with a keen interest in science, Ive always been fascinated by the invisible forces that shape our world. One such force that has captured my imagination is magnetism. Its a concept thats both simple and complex, visible yet invisible, and its all thanks to the humble magnet.Growing up, I was always intrigued by the way magnets could attract or repel each other. I remember the first time I saw a magnet lifting a paperclip. It was like magic! I couldnt understand how a small piece of metal could have such a strong pull. This curiosity led me to learn more about magnetism and its properties.Magnetism is a force of attraction or repulsion that arises from the motion of electric charges, such as electrons. Every magnet has two poles: a north pole and a south pole. Its a wellknown fact that opposite poles attract, while like poles repel each other. This is the basic principle of magnetism, but the applications of this principle are vast and varied.In school, we learned about the Earths magnetic field, which is generated by the motion of molten iron in its core. This magnetic field is what allows compasses to work, pointing towards the magnetic north pole. I was amazed to learn that the compass, a simple tool with a magnetized needle, has been guiding sailors and explorers for centuries.Magnetism also plays a crucial role in modern technology. From the hard drives that store our digital data to the motors that power our electric cars, magnets are everywhere. I was particularly fascinated by the concept ofelectromagnetic induction, which is the principle behind generators and electric motors. Its incredible to think that the simple interaction of a magnet and a coil of wire can generate electricity.One of my favorite experiments in school was creating a homemade electromagnet. All it took was a coil of wire, a battery, and an iron nail. When I connected the wire to the battery, the iron nail became a magnet, capable of attracting other metal objects. It was a simple demonstration of electromagnetism, but it was also a testament to the power of magnetism.Magnetism is not just limited to the physical world. It has also inspired many metaphors and analogies. For example, we often talk about people being magnetic personalities, drawing others towards them with their charm and charisma. Similarly, we describe strong attractions as magnetic.Despite its ubiquity, magnetism still holds many mysteries. Scientists are still researching the properties of superconducting magnets and their potential applications in medicine and energy storage. The quest for understanding the nature of magnetism is an ongoing journey of discovery.In conclusion, magnetism is a fundamental force that has shaped our world in countless ways. From the Earths magnetic field to the technology that powers our lives, the influence of magnetism is everywhere. As a high school student, I am excited to continue exploring the wonders of magnetism and the many ways it shapes our world.。

计算机专业英语单词计算机专业英语单词计算机专业英语词汇指与计算机硬件、软件、网络等多方面有关的英语词汇，主要包括硬件基础、计算机系统维护、计算机网络基础、软件、程序设计语言、计算机网络技术、IT职场英语等词汇。

下面为大家带来计算机专业英语单词，快来看看吧。

计算机专业英语单词1-10 第一单元Processor 处理机Primary storage 主存储器 bit 位hearsay 传说CPU 中英处理器control unit 控制部件arithmetic and logic unit 算术逻辑部件 integral parts 不可缺的部件 tape and disk磁带和磁盘DRAM动态随机存储器 SRAM静态随机存储器 Register 寄存器a state of the art 目前工艺水平 chip 芯片VDT 视频显示终端secondary storage 辅助存储器at a premium非常珍贵reallocate 重新分配capacity 容量coaxial cable 同轴电缆program and data 程序和数据 instruction 指令location 单元RAM随机存取存储器 Hardwired 硬连线EPROM可擦可编程只读存储器 Cache 高速缓存Throughput 吞吐量read-mostly 以读为主EEPROM电可擦编程ROM Nonvolatility 非易失性Updatable 可修改的 in place 在适当的地方 semiconductor 半导体 flash memory 闪存functionality 功能byte-level 字节级be referred to as 称作 virtually 事实上house 存放expansion 扩充peripheral 外围的slot 插槽power supply 电源 system board 系统板 storage bay 存储机架floppy 软盘第二单元optical laser disk 光盘 laser beam激光束 score 刻痕microscopic pit 微小的凹点 light-sensitive 光敏感的 deflect 偏转access arm存取臂 inviting 令人心动的 fluctuation 波动 emerge 显现stabilize 稳定gigabyte 千兆字节 cd 光盘magneto-optical disk 磁光盘 entrepreneur 企业家video 视频的拓展阅读：A(Active-matrix)主动矩阵(Adapter cards)适配卡(Advanced application)高级应用(Analytical graph)分析图表(Analyze)分析(Animations)动画(Application software) 应用软件(Arithmetic operations)算术运算(Audio-output device)音频输出设备(Access time)存取时间(access)存取(accuracy)准确性(ad network cookies)广告网络信息记录软件(administrator)管理员(Add-ons)插件(Address)地址(Agents)代理(Analog signals)模拟信号(Applets)程序(Asynchronous communications port)异步通信端口(Attachment)附件AGP(accelerated graphics port)加速图形接口ALU (arithmetic-logic unit)算术逻辑单元AAT(Average Access Time) 平均存取时间ACL(Access Control Lists)访问控制表ACK(acknowledgement character)确认字符ACPI (Advanced Configuration and Power Interface)高级配置和电源接口ADC(Analog to Digital Converter)模数转换器ADSL(Asymmetric Digital Subscriber Line)非对称用户数字线路ADT(Abstract Data Type)抽象数据类型AGP(Accelerated Graphics Port)图形加速端口AI(Artif icial Intelligence)人工智能AIFF(Audio Image File Format)声音图像文件格式ALU(Arithmetic Logical Unit) 算术逻辑单元AM(Amplitude Modulation)调幅ANN(Artificial Neural Network)人工神经网络ANSI(American National Standard Institute)美国国家标准协会API(Application Programming Interface)应用程序设计接口APPN(Advanced Peer-to-Peer Network)高级对等网络ARP(Address Resolution Protocol)地址分辨/ 转换协议ARPG(Action Role Playing Game)动作角色扮演游戏ASCII (American Standard Code for Information Interchange)美国信息交换标准代码ASP(Active Server Page)活动服务器网页ASP(Application Service Provider)应用服务提供商AST(Average Seek Time)平均访问时间ATM(asynchronous transfer mode)异步传输模式ATR (Automatic Target Recognition) 自动目标识别AVI (Audio Video Interleaved)声音视频接口B(Bar code)条形码(Bar code reader)条形码读卡器(Basic application)基础程序(Binary coding schemes)二进制编码方案(Binary system)二进制系统(Bit)比特(Browser)浏览器(Bus line)总线(Backup tape cartridge units)备份磁带盒单元(Bandwidth)带宽(Bluetooth)蓝牙(Broadband)宽带(Bus)总线B2B(Busines s to Business)商业机构对商业机构的电子商务B2C(Business to Consumer)商业机构对消费者的电子商务BBS(bulletin board system)电子公告牌系统BER(Bit Error Rate)误码率BFS (Breadth First Search) 广度优先搜索BGP(Border Gateway Protocol)边缘网关协议BIOS(basic input/output system)基本输入输出系统BISDN(Broadband- Integrated Services Digital Network)宽带综合业务数字网BLU(Basic Link Unit)基本链路单元BOF(Beginning Of File)文件开头BPS(Bits Per Second)每秒比特数BRI(Basic Rate Interface)基本速率接口BSP(Byte Stream Protocol)字节流协议BSS(Broadband Switching System)宽带交换系统C(Cables)连线(Cell)单元箱(Chain printer)链式打印机(Character and recognition device)字符标识识别设备(Chart)图表(Chassis)支架(Chip)芯片(Clarity)清晰度(Closed architecture)封闭式体系结构(Column)列(Combination key)结合键(computer competency)计算机能力(connectivity)连接，结点(Continuous-speech recognition system)连续语言识别系统(Control unit)操纵单元(Cordless or wireless mouse)无线鼠标(Cable modems)有线调制解调器(Channel)信道(Chat group)谈话群组(Client)客户端(Coaxial cable)同轴电缆(cold site)冷网站(Commerce servers)商业服务器(Communication channel)信道(Communication systems)信息系统CD(Compact disc)光盘(computer abuse amendments act of 19941994)计算机滥用法案(computer crime)计算机犯罪(computer ethics)计算机道德(computer fraud and abuse act of 1986)计算机欺诈和滥用法案(computer matching and privacy protection act of 1988)计算机查找和隐私保护法案(Computer network)计算机网络(computer support specialist)计算机支持专家(computer technician)计算机技术人员(computer trainer)计算机教师(Connection device)连接设备(Connectivity)连接(cookies-cutter programs)信息记录截取程序(cookies)信息记录程序(cracker)解密高手(Cyber cash)电子货币(Cyberspace)计算机空间(chart)图表(closed architecture )封闭式体系结构C2C(Consumer-to-consumer)个人对个人CPU (central processing unit)中央处理器CISC (complex instruction set computer)复杂指令集计算机CRT( cathode-ray tube)阴极射线管AD(Computer Aided Design)计算机辅助设计CAE(Computer-Aided Engineering)计算机辅助工程CAI(Computer Aided Instruction)计算机辅助教学CAM(Computer Aided Manufacturing)计算机辅助管理CASE(Computer Assisted Software Engineering)计算机辅助软件工程CAT(Computer Aided Test)计算机辅助测试CATV(Community Antenna Television)有线电视CB(control bus)控制总线CCP(Communication Control Procrssor)通信控制处理机CD(Compact Disc)压缩光盘，只读光盘CD-R(Compact Disc-Recordable)可录光盘，只写一次的光盘CDFS(Compact Disk File System)密集磁盘文件系统CDMA(Code Division Multiple Access)码分多路访问CD-MO(Compact Disc-Magneto Optical)磁光式光盘CD-ROM(compact disc read-only memory)只读光盘CD-RW(compact disc rewritable)可读写光盘CGA(Color Graphics Adapter)彩色显示器CGI(common gateway interface)公共网关接口CI(Computational Intelligence)计算智能CISC(Complex Instruction Set Computer) 复杂指令集计算机CMOS(Complementary Metal Oxide Semiconductor)互补金属氧化物半导体存储器COM(Component object model)组件对象模型CORBA(Common Object Request Broker Architecture)公共对象请求代理结构CPU(central proces sing unit)中央处理单元CRC(cyclical redundancy check)循环冗余校验码CRM(Client Relation Management)客户关系管理CRT(Cathode-Ray Tube)阴极射线管,显示器CSMA(Carrier Sense Multi -Access)载波侦听多路访问CSU(Channel Service Unit)信道服务单元CU(Control Unit)控制单元DDB(Database)数据库(database files)数据库文件(Database manager)数据库管理DBMS(Database manager system)数据库管理系统(Data bus)数据总线(Data projector)数码放映机(Desktop system unit)台式电脑系统单元(Destination file)目标文件(Digital cameras)数码照相机(Digital notebooks)数字笔记本(Digital video camera)数码摄影机(Discrete-speech recognition system)不连续语言识别系统(Document)文档(document files)文档文件(Dot-matrix printer)点矩阵式打印机(Dual-scan monitor)双向扫描显示器(Dumb terminal)非智能终端(data security)数据安全(Data transmission specifications)数据传输说明(database administrator)数据库管理员(Data play)数字播放器(Demodulation)解调(denial of service attack)拒绝服务攻击(Dial-up service)拨号服务(Digital cash)数字现金(Digital signals)数字信号(Digital subscriber line)数字用户线路(Digital versatile disc)数字化通用磁盘(Digital video disc)数字化视频光盘(Direct access)直接存取(Directory search)目录搜索(disaster recovery plan)灾难恢复计划(Disk caching)磁盘驱动器高速缓存(Diskette)磁盘(Disk)磁碟(Distributed data processing system)分部数据处理系统(Distributed processing)分布处理(Domain code)域代码(Downloading)下载DVD(Digital Versatile Disc)数字多功能光盘DVD-R(DVD-Recordable)可写DVDDVD-RAM(DVD- Random Access Memory)DVD随机存取器DNS(Domain name system)域名服务器DAC(Digital to Analogue Converter)数模转换器DAO(Data Access Object)数据访问对象DAP(Directory Acces s Protocol)目录访问协议DBMS(Database Management System)数据库管理系统DCE(data communication equipment)数据通信设备DCE(Distributed Computing Environment)分布式计算环境DCOM(Distributed COM)分布式组件对象模型DDB(Distributed DataBase)分布式数据库DDE(Dynamic Data Exchange)动态数据交换DDI(Device Driver Interface)设备驱动程序接口DDK(Driver Development Kit)驱动程序开发工具包DDN(Data Digital Network)数据数字网DEC(Digital Equipment Corporation)数字设备公司DES(Data Encryption Standard)数据加密标准DFS(Depth First Search) 深度优先搜索DFS(Distributed File System)分布式文件系统DHCP(Dynamic Host Configuration Protocol)动态主机配置协议DIB(Dual Independent Bus)双独立总线DIC(Digital Image Control)数字图像控制DLC(Data Link Control)数据链路控制DLL(Dynamic Link Library)动态链接库DLT(Data Link Terminal)数据链路终端DMA(Direct Memory Access)直接内存访问DMSP(Distributed Mail System Protocol)分布式电子邮件系统协议DNS(Domain Name System)域名系统DOM(Document Object Mode)文档对象模型DOS(Disk Operation System)磁盘操作系统DQDB(Distributed Queue Dual Bus)分布式队列双总线DRAM(Dynamic Random Access Memory)动态随机存取存储器DSD(Direct Stream Digital)直接数字信号流DSL(Digital Subscriber Line)数字用户线路DSM(Distributed Shared Memory)分布式共享内存DSP(Digital Signal Processing)数字信号处理DTE(Data Terminal Equipment)数据终端设备DVD(Digital Versatile Disc)数字多功能盘DVD-ROM(DVD-Read Only Memory)计算机用只读光盘DVI(Digital Video Interactive)数字视频交互E(e-book)电子阅读器(Expansion cards)扩展卡(end user)终端用户(e-cash)电子现金(e-commerce)电子商务(electronic cash)电子现金(electronic commerce)电子商务(electronic communications privacy act of1986)电子通信隐私法案(encrypting)加密术(energy star)能源之星(Enterprise computing)企业计算化(environment)环境(Erasable optical disks)可擦除式光盘(ergonomics)人类工程学(ethics)道德规范(External modem)外置调制解调器(extranet)企业外部网EC(Embedded Controller)嵌入式控制器EDIF(Electronic Data Interchange Format)电子数据交换格式EEPROM(Erasable and Electrically Programmable ROM)电擦除可编程只读存储器EGA(Enhanced Graphics Adapter)彩色显示器,分辨率为640×350 ,可以显示 16 种颜色EGP(External Gateway Protocol)外部网关协议EISA(Extended Industry Standard Architecture)增强工业标准结构EMS(Expanded Memory Specification)扩充存储器规范EPH(Electronic payment Handler)电子支付处理系统EPROM(Erasable Programmable ROM)可擦除可编程只读存储器ERP(Enterprise Resource Planning)企业资源计划ETM(ExTended Memory)扩展存储器F(Fax machine)传真机(Field)域(Find)搜索(FireWire port)火线端口(Firmware)固件(Flash RAM)闪存(Flatbed scanner)台式扫描器(Flat-panel monitor)纯平显示器(floppy disk)软盘(Formatting toolbar)格式化工具条(Formula)公式(Forum)论坛(Function)函数(fair credit reporting act of 1970)公平信用报告法案(Fiber-optic cable)光纤电缆(File compression)文件压缩(File decompression)文件解压缩(filter)过滤(firewall)防火墙(firewall)防火墙(Fixed disk)固定硬盘(Flash memory)闪存(Flexible disk)可折叠磁盘(Floppies)磁盘(Floppy-disk cartridge)磁盘盒(Formatting)格式化(freedom of information act of 1970)信息自由法案(frequency)频率(frustrated)受挫折(Full-duplex communication)全双通通信FAT(File Allocation Table)文件分配表FCB(File Control Block)文件控制块FCFS(First Come First Service)先到先服务FCS(Frame Check Sequence)帧校验序列FDD(Floppy Disk Device)软盘驱动器FDDI(Fiber-optic Data Distribution Inter face)光纤数据分布接口FDM(Frequency-Division Multiplexing)频分多路FDMA(Frequency Division Multiple Address)频分多址FEC(Forward Error Correction) 前向纠错FEK(File Encryption Key)文件密钥FEP(Front Ef fect Processor)前端处理机FET(Field Effect Transistor)场效应晶体管FIFO(First In First Out)先进先出FM(Frequency Modulation)频率调制FPU(Float Point Unit)浮点部件FRC(Frame Rate Control)帧频控制FTAM(File Transfer Access and Management)文件传输访问和管理FTP(File Transfer Protocol)文件传输协议G(General-purpose application)通用运用程序(Gigahertz)千兆赫(Graphic tablet)绘图板(green pc)绿色个人计算机(Group by) 排序GAL(General Array Logic)通用逻辑阵列GCR(Group-Coded Recording)成组编码记录GDI(Graphics Device Interface)图形设备接口GIF(Graphics Interchange Format)一种图片文件格式,图形转换格式GIS(Geographic Information System)地理信息系统GPI(Graphical Programming Interface)图形编程接口GPIB(General Purpose Interface Bus)通用接口总线GPS(Global Positioning System)全球定位系统GSX(Graphics System Extension)图形系统扩展GUI(Graphical User Interface)图形用户接口H(handheld computer)手提电脑(Hard copy)硬拷贝(hard disk)硬盘(hardware)硬件(Help)帮助(Host computer)主机(Home page)主页(Hyperlink)超链接(hacker)黑客(Half-duplex communication)半双通通信(Hard-disk cartridge)硬盘盒(Hard-disk pack)硬盘组(Head crash)磁头碰撞(header)标题(help desk specialist)帮助办公专家(helper applications)帮助软件(Hierarchical network)层次型网络(history file)历史文件(hits)匹配记录(horizontal portal)横向用户(hot site)热网站(Hybrid network)混合网络HPSB (high performance serial bus)高性能串行总线HDTV(high-definition television)高清晰度电视HDC(Hard Disk Control)硬盘控制器HDD(Hard Disk Drive)硬盘驱动器HDLC(High-level Data Link Control)高级数据链路控制HEX(HEXadecimal)十六进制HPFS(High Performance File System)高性能文件系统HPSB(High Performance Serial Bus)高性能串行总线HTML(Hyper Text Markup Language)超文本标记语言HTTP(Hyper Text Transport Protocol)超文本传输协议I(Image capturing device)图像获取设备IT(information technology)信息技术(Ink-jet printer)墨水喷射印刷机(Integrated package)综合性组件(Intelligent termina)l智能终端设备(Intergrated circuit)集成电路(implements )实现接口(Interface cards)接口卡(Internal modem)内部调制解调器(internet telephony)网络电话(internet terminal)互联网终端(Identification)识别(i-drive)网络硬盘驱动器(illusion of anonymity)匿名幻想(index search)索引搜索(information pushers)信息推送器(initializing )初始化(instant messaging)计时信息(internal hard disk)内置硬盘(Internet hard drive) 网络硬盘驱动器(intranet)企业内部网ISA (industry standard architecture)工业标准结构体系IRC(internet relay chat)互联网多线交谈IAC(Inter-Application Communications)应用间通信IC(Integrated Circuit)集成电路ICMP(Internet Control Mes sage Protocol)因特网控制消息协议ICP(Internet Content Provider)因特网内容服务提供商,是 ISP中提供信息服务的一种机构IDC(International Development Center)国际开发中心IDE(Integrated Development Environment)集成开发环境IDL(Interface Definition Language)接口定义语言IEEE(Institute of Electrical and Electronics Engineering)电子电器工程师协会IGP(Interior Gateway Protocol)内部网关协议IIS(Internet Information Service)因特网信息服务IP(Internet Protocol)因特网协议IPC(Inter-Process Communication)进程间通信IPSE(Integrated Project Support Environments)集成工程支持环境IPX(Internet Packer Exchitecture)互联网报文分组交换ISA(Industry Standard Architecture)工业标准结构,是 IBM PC/ XT总线标准ISDN(Integrated Service Digital Network)综合业务数字网ISO(International Standard Organization)国际标准化组织ISP(Internet Service Provider)因特网服务提供者ITU(International Telecom Union)国际电信联盟J(joystick)操纵杆JDBC(Java Database Connectivity) J ava数据库互联JPEG(Joint Photographic Experts Group)联合图片专家组JSP(Java Server Page) Java 服务器页面技术JVM(Java Virtual Machine)Java虚拟机K(keyword search)关键字搜索KB(Kilobyte)千字节KBPS(Kilobits Per Second)每秒千比特KMS(Knowledge Management System)知识管理系统L(laser printer)激光打印机(Layout files)版式文件(Light pen)光笔(Locate)定位(Logical operations)逻辑运算(Lands)凸面(Line of sight communication)视影通信(Low bandwidth)低带宽(lurking)潜伏LCD (liquid crystal display monitor)液晶显示器LAN(Local Area Network)局域网LBA(Logical Block Addressing)逻辑块寻址LCD(Liquid Crystal Display)液晶显示器LDT(Logic Design Translator)逻辑设计翻译程序LED(Light Emitting Diode)发光二极管LIFO(Last In First Out)后进先出LP(Linear Programming)线性规划LPC(Local Procedure Call)局部过程调用LSIC(Large Scale Integration Circuit)大规模集成电路M(Main board)主板(Mark sensing)标志检测(Mechanical mouse)机械鼠标(Memory)内存(Menu)菜单(Menu bar)菜单栏(Microprocessor)微处理器(Microseconds)微秒(Modem card)调制解调器(Monitor)显示器(Motherboard)主板(Mouse) 鼠标(Multifunctional device)多功能设备(Magnetic tape reels)磁带卷(Magnetic tape streamers)磁带条(mailing list)邮件列表(Medium band)媒质带宽(metasearch engine)整合搜索引擎(Microwave)微波(Modem)解调器(Modulation)解调MAN(Metropolitan area network)城域网MICR(magnetic-ink character recognition)磁墨水字符识别器MAC(Medium Access Control)介质访问控制MAN(Metropolitan Area Network)城域网MBR(Master Boot Record)主引导记录MC(Memory Card)存储卡片MCA(Micro Channel Architecture)微通道结构MDA(Monochrome Display Adapter)单色显示适配卡MFM(Modified Frequency Modulation)改进调频制MIB(Management Information Bass)管理信息库MIDI(Musical Instrument Digital Interface) 乐器数字接口MIMD(Multiple Instruction Stream,Multiple Data Stream)多指令流,多数据流MIPS(Million Instructions Per Second)每秒百万条指令MIS(Management Information System)管理信息系统MISD(Multiple Instruction Stream,Single Data Stream)多指令流,单数据流MMDS(Multi-channel Multipoint Distribution Service)多波段多点分发服务器MMU(Memory Management Unit)内存管理单元MPC(Multimedia PC)多媒体计算机MPEG(Moving Picture Expert Group) 一种视频和音频的.国际标准格式MPLS(Multi-Protocol Label Switching)多协议标记交换MPS(Micro Processor System)微处理器系列MTBF(Mean Time Between Failures)平均故障间隔时间MUD(Multiple User Dimension)多用户空间N(Net PC)网络计算机(Network adapter card)网卡(Network personal computer)网络个人电脑(Network terminal)网络终端(Notebook computer)笔记本电脑(Notebook system unit)笔记本系统单元(Numeric entry)数字输入(national information infrastructure protection act of1996)国际信息保护法案(national service provider)全国性服务供应商(Network architecture)网络体系结构(Network bridge)网桥(Network gateway)网关(network manager)网络管理员(newsgroup)新闻组(no electronic theft act of1997)无电子盗窃法(Node)节点(Nonvolatile storage)非易失性存储NOS(Network operation system)网络操作系统NAOC(No-Account Over Clock)无效超频NAT(Network Address Translation) 网络地址转换NC(Network Computer)网络计算机NDIS(Network Device Interface Speci fication)网络设备接口规范NCM(Neural Cognitive Maps)神经元认知图NFS(Network File System)网络文件系统NIS(Network Information Services)网络信息服务NNTP(Network News Transfer Protocol)网络新闻传输协议NOC(Network Operations Center) 网络操作中心NSP(Name Server Protocol)名字服务器协议NTP(Network Time Protocol)网络时间协议NUI(network user identification)网络用户标识O(Object embedding)对象嵌入(Object linking)目标链接(Open architecture)开放式体系结构OS(Operation System)操作系统(Optical disk)光盘(Optical mouse)光电鼠标(Optical scanner)光电扫描仪(Outline)大纲(off-line browsers)离线浏览器(Online storage)联机存储OLE (object linking and embedding)对象链接入OCR(optical-character recognition)字符识别器OMR(optical-mark recognition)光标阅读器OA(Of f ice Automation)办公自动化OCR(Optical Character Recognition)光学字符识别ODBC(Open Database Connectivity)开放式数据库互联ODI(Open Data- link Interface)开放式数据链路接口OEM(Original Equipment Manufactures)原始设备制造厂家OLE(Object Linking and Embedding)对象链接与嵌入OMG(Object Management Group)对象管理组织OMR(Optical-Mark Recognition)光标阅读器OOM(Object Oriented Method)面向对象方法OOP(Object Oriented Programming)面向对象程序设计ORB(Object Request Broker)对象请求代理OS(Operating System)操作系统OSI(Open System Interconnect Reference Model)开放式系统互联参考模型OSPF(Open Shortest Path First)开发最短路径优先P(palmtop computer)掌上电脑(Parallel ports)并行端口(Passive-matrix)被动矩阵(PC card)个人计算机卡(Personal laser printer)个人激光打印机(Personal video recorder card)个人视频记录卡(Photo printer)照片打印机(Pixel)像素(Platform scanner)平版式扫描仪(Plotter)绘图仪(Plug and play)即插即用(Plug-in boards)插件卡(Pointer)指示器(Pointing stick)指示棍(Port)端口(Portable scanner)便携式扫描仪(Presentation files)演示文稿(Presentation graphics)电子文稿程序(Primary storage)主存(Procedures)规程(Processor)处理机(Programming control language)程序控制语言(Packets)数据包(Parallel data transmission)平行数据传输(Peer-to-peer network system点)对点网络系统(person-person auction site)个人对个人拍卖站点(physical security)物理安全(Pits)凹面(plug-in)插件程序(privacy )隐私权(proactive )主动地(programmer)程序员(Protocols)协议(provider)供应商(project )项目工程(proxy server)代理服务(pull products)推取程序(push products)推送程序PDA(personal digital assistant)个人数字助理PCI(peripheral component interconnect)外部设备互连总线PCMCIA (Personal Memory Card International Association)个人计算机存储卡国际协会PBX(Private Branch Exchange)用户级交换机PC(Personal Computer)个人计算机PCB(Process Control Block)进程控制块PCI(Peripheral Component Interconnect)外部连接互联,是一种局部总线PCM(Pulse Code Modulation)脉冲编码调制PCS(Personal Communications Service) 个人通信业务PDA(Personal Digital As sistant)个人数字助理PDF(Portable Document Format)便携式文档格式PDN(Public Data Network)公共数据网PHP(Personal Home Page)个人网页PIB(Programmable Input Buffer)可编程输入缓冲区PMMU(Paged Memory Management Unit)页面存储管理单元POP(Post Of f ice Protocol)邮局协议POST(Power-On Self -Test)加电自检PPP(Peer-Peer Protocol)端对端协议PPP(Point to Point Protocol)点到点协议PPSN(Public Packed-Switched Network)公用分组交换网PR(Performance Rate)性能比率PROM(Programmable ROM)可编程只读存储器PSN(Processor Serial Number)处理器序列号QQC(Quality Control)质量控制QLP(Query Language Proces sor)查询语言处理器QoS(Quality of Service)服务质量R(RAM cache)随机高速缓冲器(Range)范围(Record)记录(Relational database)关系数据库(Replace)替换(Resolution)分辨率(Row)行(Read-only)只读(Reformatting)重组(regional service provider)区域性服务供应商(reverse directory)反向目录(right to financial privacy act of 1979)财产隐私法案(Ring network)环形网RAD(Rapid Application Development)快速应用开发RAI(Remote Application Interface)远程应用程序界面RAID(Redundant Array Independent Disk) 冗余列阵磁盘机RARP(Reverse Address Resolution Protocol)反向地址解析协议RAM(Random Acces s Memory)随机存储器RAM(Real Address Mode)实地址模式RAID(Redundant Arrays of Inexpensive Disks)冗余磁盘阵列技术RAS(Remote Access Service)远程访问服务RCP(Remote CoPy)远程复制RDA(Remote Data Access)远程数据访问RDO (Remote Data Objects) 远程数据对象RF(Radio Frequency) 射频，无线电频率RIP(Raster Image Protocol)光栅图像处理器RIP(Routing Information Protocol)路由选择信息协议RISC(Reduced Instruction Set Computer)精简指令集计算机ROM(Read Only Memory)只读存储器RPC(Remote Procedure Call)远程过程调用RPG(Role Play Games)角色扮演游戏RPM(Revolutions Per Minute)转/分RTS(Request To Send)请求发送RTSP(Real Time Streaming Protocol) 实时流协议S(Scanner)扫描器(Search)查找(Secondary storage device)辅助存储设备(Semiconductor)半导体(Serial ports)串行端口(Server)服务器(Shared laser printer)共享激光打印机(shakedown test )调试(Sheet)表格(Silicon chip)硅片(Slots)插槽(Smart card)智能卡(Soft copy)软拷贝(Software suite)软件协议(Sorting)排序(Source file)源文件(Special-purpose application)专用文件(Spreadsheet)电子数据表(Standard toolbar)标准工具栏(Supercomputer)巨型机(System )系统(System cabinet )系统箱(System clock)时钟(System software)系统软件(Satellite/air connection services)卫星无线连接服务(search engines)搜索引擎(search providers)搜索供应者(search services )搜索服务器(Sectors)扇区(security)安全(Sending and receiving devices)发送接收设备(Sequential access)顺序存取(Serial data transmission)单向通信(signature line)签名档(snoopware)监控软件(software copyright act of1980)软件版权法案(software piracy)软件盗版(Solid-state storage)固态存储器(specialized search engine)专用搜索引擎(spiders)网页爬虫(spike)尖峰电压(Star network)星型网(Strategy)方案(subject)主题(subscription address)预定地址(Superdisk)超级磁盘(surfing)网上冲浪(surgeprotector)浪涌保护器(systems analyst)系统分析师...SACL(System Access Control List) 系统访问控制列表SAF(Store And Forward)存储转发SAP(Service Acces s Point)服务访问点SCSI(Small Computer System Interface)小型计算机系统接口SDLC(Synchronous Data Link Control)同步数据链路控制SGML(Standard Generalized Markup Language)标准通用标记语言SHTTP(Secure Hype Text Transfer Protocol)安全超文本传递协议SMP(Symmetric Multi-Processor)对称式多处理器SMTP(Simple Mail Transport Protocol)简单邮件传输协议SNA(System Network Architecture)系统网络结构SNMP(Simple Network Management Protocol)简单网络管理协议SNR(Signal Noise Ratio)信噪比SNTP(Simple Network Time Protocol)简单网络时间协议SONC(System On a Chip)系统集成芯片SONET(Synchronous Optic Network)同步光纤网SPC(Stored-Program Control)存储程序控制SQL(Structured Query Language)结构化查询语言SRAM(Static Random Access Memory)静态随机存储器SRPG(Strategies Role Play Games) 战略角色扮演游戏SSL(Secure Sockets Layer)安全套接层STDM(Synchronous Time Division Multiplexing)同步时分复用STG(Shoot Game)射击类游戏STP(Shielded Twisted-Pair)屏蔽双绞线SVGA (Super Video Graphics Array) 超级视频图形阵列T(Table)二维表(Telephony)电话学(Television boards)电视扩展卡(Terminal) 终端(Template)模板(Text entry)文本输入(Thermal printer )热印刷(Thin client)瘦客(Toggle key)触发键(Toolbar)工具栏(Touch screen)触摸屏(Trackball)球(TV tuner card)电视调谐卡(Two-state system))双状态系统(technical writer)技术协作者(technostress)重压技术(telnet)远程登录(Time-sharing system)分时系统(Topology)拓扑结构(Tracks)磁道(traditional cookies)传统的信息记录程序(Twisted pair)双绞TCB(Transmission Control Block)传输控制块TCP(Transmis sion Control Protocol)传输控制协议TCP/IP(Transmission Control Protocol / Internet Protocol)传输控制协议/ 网间协议TDM(Time Division Multiplexing)时分多路复用TDMA(Time Division Multiplexing Address)时分多址技术TDR(Time-Domain Reflectometer)时间域反射测试仪TFT(Thin Film Transistor Monitor)薄膜晶体管显示器TFTP(Trivial File Transfer Protocol)简单文件传送协议TIFF(Tag Image File Format)标记图形文件格式TIG(Task Interaction Graph)任务交互图TLI(Transport Layer Interface)传输层接口TM(Traffic Management)业务量管理，流量管理TPS(Transactions Per Second)(系统)每秒可处理的交易数TSR(Terminate and Stay Resident)终止并驻留TTL(Transistor-Transistor Logic)晶体管—晶体管逻辑电路TWX(Teletypewriter Exchange)电传电报交换机U(Unicode)统一字符标准(uploading)上传(usenet)世界性新闻组网络UART(Universal Asynchronous Receiver Transmitter)通用异步收发器UDF(Universal Disk Format)通用磁盘格式UDP(User Datagram Protocol)用户数据报协议UHF(Ultra High Frequency)超高频UI(User Interface)用户界面，用户接口UIMS(User Interface Management System)用户接口管理程序UNI(User Network Interface)用户网络接口UPA(Ultra Port Architecture)超级端口结构UPS(Uninterruptible Power Supply)不间断电源URI(Uniform Resource Identi fier)环球资源标识符URL(Uniform Resource Locator)统一资源定位器USB(Universal Serial Bus)通用串行总线UTP(Unshielded Twisted-Pair)非屏蔽双绞线UXGA(Ultra Extended Graphics Array)超强图形阵列V(Virtual memory)虚拟内存(Video display screen)视频显示屏(Voice recognition system)声音识别系统(vertical portal)纵向门户(video privacy protection act of 1988)视频隐私权保护法案(virus checker)病毒检测程序(virus)病毒(Voiceband)音频带宽(Volatile storage)易失性存储(voltage surge)电涌VAD(Virtual Addres s Descriptors)虚拟地址描述符VAGP(Variable Aperature Grille Pitch) 可变间距光栅VAN(Value Added Network)增值网络VAP(Value-Added Process)增值处理VAS(Value-Added Server)增值服务VAX(Virtual Address eXtension)虚拟地址扩充VBR(Variable Bit Rate)可变比特率VC(Virtual Circuit)虚拟线路VCPI(Virtual Control Program Interface)虚拟控制程序接口VDD(Virtual Device Driver s)虚拟设备驱动程序VDR(Video Disc Recorder)光盘录像机VDT(Video Display Terminals)视频显示终端VDU(Visual Display Unit)视频显示单元VFS(Virtual File System)虚拟文件系统VGA(Video Graphics Adapter)视频图形适配器VIS(Video Information System)视频信息系统VLAN(Virtual LAN)虚拟局域网VLIW(Very Long Instruction Word)超长指令字VLSI(Very Large Scale Integration)超大规模集成VMS(Virtual Memory System)虚拟存储系统VOD(Video On Demand)视频点播系统VON(Voice On Net)网上通话VR(Virtual Reality)虚拟现实VRML(Virtual Reality Modeling Language)虚拟现实建模语言VRR(Vertical Refresh Rate)垂直刷新率VTP(Virtual Terminal Protocol)虚拟终端协议W(Wand reader )条形码读入(Web )网络(Web appliance )环球网设备(Web page)网页(Web site address)网络地址(Web terminal)环球网终端(Webcam)摄像头(What-if analysis)假定分析(Wireless revolution)无线革命(Word)字长(Word processing)文字处理(Word wrap)自动换行(Worksheet file) 工作文件(web auctions)网上拍卖(web broadcasters)网络广播(web portals)门户网站(web sites)网站(web storefront creation packages)网上商店创建包(web storefronts)网上商店(web utilities)网上应用程序(web-downloading utilities)网页下载应用程序(webmaster web)站点管理员(web)万维网(Wireless modems)无线调制解调器(wireless service provider)无线服务供应商WWW(world wide web)万维网(worm)蠕虫病毒(Write-protect notch)写保护口WAN(Wide area network)广域网(Web server)Web 服务器(well-connected )连接良好(well-known services )公认的服务(wildcard character)通配符(wildcarding )通配符方式(window menu )窗口菜单(Windows 2000 Task Manager)Windows 2000任务管理器WINS(Windows Internet Name Service)Windows Internet 命名服务WMI(Windows Management Instrumentation) Windows 管理规范(Windows Media Services)Windows Media 服务(WINS proxy)WINS 代理(WINS resource )WINS 资源(wireless communication )无线通讯WMI(Windows Management Instrumentation ) Windows 管理规范(workgroup)工作组WAN(Wide Area Network)广域网WAE(Wireles s Application Environment)无线应用环境WAIS(Wide Area Information Service)广义信息服务,数据库检索工具WAP(Wireles s Application Protocol)无线应用协议WAV(Wave Audio Format)非压缩的音频格式文件WDM(Wavelength Division Multiplexing)波分多路复用WDP(Wireless Datagram Protocol)无线数据包协议WFW(Windows for Workgroups)工作组窗口WML(Wireles s Markup Language)无线标记语言WMP(Windows Media Player)Windows媒体播放器WORM(Write Once, Read Many time)写一次读多次光盘。

专利名称：Advanced digital flux gate magnetometer 发明人：Paul L. Feintuch,Eric K. Slater,Kirk Kohnen 申请号：US08/636420申请日：19960423公开号：US05652512A公开日：19970729专利内容由知识产权出版社提供摘要：Digital logic comprising a high speed analog to digital converter, a high speed analog to digital converter, a digital multiplier, and an infinite impulse response filter and decimation circuit are used to digitize a magnetic signal that is subsequently processed by magnetic data processing algorithms. The high resolution digital to analog converter is directly incorporated in a feedback loop of a magnetometer sensor, and an expensive precision analog to digital converter is replaced by a less expensive, lower power digital to analog converter. The improvement provided by the present invention includes a high speed analog to digital converter coupled between the oscillator and a first input of a multiplier, and a second analog to digital converter that is coupled between the sense coil of the sensor and a second input of the multiplier. The output of the multiplier is coupled to an infinite impulse response filter and decimation circuit that produces the digital output signal from the magnetometer. The output of the infinite impulse response filter and decimation circuit is coupled by way of a digital to analog converter to the feedback coil of the sensor. Depending on the system requirements, the two analog to digital converters, the digital multiplier, and the infinite impulse response filter and decimation circuit may be implemented in one readily available microcontroller at low cost. This serves to reduce the number of components, complexity, and expense ofthe magnetometer.申请人：HUGHES AIRCRAFT COMPANY代理人：G. S. Grunebach,M. W. Sales,W. K. Denson-Low 更多信息请下载全文后查看。

数电票的外文文献Title: The Evolution of Digital Tickets in Electrical EngineeringIntroduction:Digital tickets have revolutionized the field of electrical engineering, offering numerous benefits and advancements. This article explores the evolution of digital tickets in the context of electrical engineering, highlighting their significance and impact on various aspects of the industry.1. The Emergence of Digital Tickets:The advent of digital technology has paved the way for the development of digital tickets in electrical engineering. These tickets serve as electronic records, replacing traditional paper-based tickets. The transition from physical to digital tickets has streamlined processes, facilitating efficient management and documentation of projects.2. Enhancing Efficiency and Accuracy:Digital tickets have significantly improved efficiency and accuracy in electrical engineering. With digital records, professionals can easily access and retrieve information, reducing the time spent searching for relevant data. Moreover, the risk of errors and misinterpretation is minimized, ensuring that projects are executed with precision andreliability.3. Real-time Monitoring and Analysis:One of the key advantages of digital tickets is the ability to monitor and analyze data in real-time. Electrical engineers can track project progress, monitor equipment performance, and identify potential issues promptly. This real-time monitoring enables proactive problem-solving, minimizing downtime and optimizing overall efficiency.4. Collaboration and Communication:Digital tickets have revolutionized collaboration and communication within electrical engineering teams. Through online platforms and tools, professionals can easily share and update project information, ensuring that all stakeholders are on the same page. This seamless collaboration enhances teamwork, improves productivity, and fosters innovation.5. Security and Data Protection:Digital tickets prioritize security and data protection in electrical engineering projects. With robust encryption and authentication mechanisms, sensitive project information is safeguarded from unauthorized access. Additionally, digital backups and redundancy measures ensure that data is not lost or compromised, providingpeace of mind to professionals and clients alike.6. Environmental Sustainability:The adoption of digital tickets contributes to environmental sustainability in electrical engineering. By eliminating the need for paper tickets, the industry reduces its carbon footprint and minimizes waste. This eco-friendly approach aligns with the global movement towards sustainability and showcases the industry's commitment to responsible practices.Conclusion:The evolution of digital tickets in electrical engineering has revolutionized the field, offering numerous benefits and advancements. From enhancing efficiency and accuracy to enabling real-time monitoring and analysis, digital tickets have transformed the way projects are managed and executed. Furthermore, they have fostered collaboration, improved security, and contributed to environmental sustainability. As the industry continues to embrace digital transformation, the future holds even more exciting possibilities for digital tickets in electrical engineering.。

华中师范大学物理学院物理学专业英语仅供内部学习参考！2014一、课程的任务和教学目的通过学习《物理学专业英语》，学生将掌握物理学领域使用频率较高的专业词汇和表达方法，进而具备基本的阅读理解物理学专业文献的能力。

通过分析《物理学专业英语》课程教材中的范文，学生还将从英语角度理解物理学中个学科的研究内容和主要思想，提高学生的专业英语能力和了解物理学研究前沿的能力。

培养专业英语阅读能力，了解科技英语的特点，提高专业外语的阅读质量和阅读速度；掌握一定量的本专业英文词汇，基本达到能够独立完成一般性本专业外文资料的阅读；达到一定的笔译水平。

要求译文通顺、准确和专业化。

要求译文通顺、准确和专业化。

二、课程内容课程内容包括以下章节：物理学、经典力学、热力学、电磁学、光学、原子物理、统计力学、量子力学和狭义相对论三、基本要求1.充分利用课内时间保证充足的阅读量（约1200~1500词/学时），要求正确理解原文。

2.泛读适量课外相关英文读物，要求基本理解原文主要内容。

3.掌握基本专业词汇（不少于200词）。

4.应具有流利阅读、翻译及赏析专业英语文献，并能简单地进行写作的能力。

四、参考书目录1 Physics 物理学 (1)Introduction to physics (1)Classical and modern physics (2)Research fields (4)V ocabulary (7)2 Classical mechanics 经典力学 (10)Introduction (10)Description of classical mechanics (10)Momentum and collisions (14)Angular momentum (15)V ocabulary (16)3 Thermodynamics 热力学 (18)Introduction (18)Laws of thermodynamics (21)System models (22)Thermodynamic processes (27)Scope of thermodynamics (29)V ocabulary (30)4 Electromagnetism 电磁学 (33)Introduction (33)Electrostatics (33)Magnetostatics (35)Electromagnetic induction (40)V ocabulary (43)5 Optics 光学 (45)Introduction (45)Geometrical optics (45)Physical optics (47)Polarization (50)V ocabulary (51)6 Atomic physics 原子物理 (52)Introduction (52)Electronic configuration (52)Excitation and ionization (56)V ocabulary (59)7 Statistical mechanics 统计力学 (60)Overview (60)Fundamentals (60)Statistical ensembles (63)V ocabulary (65)8 Quantum mechanics 量子力学 (67)Introduction (67)Mathematical formulations (68)Quantization (71)Wave-particle duality (72)Quantum entanglement (75)V ocabulary (77)9 Special relativity 狭义相对论 (79)Introduction (79)Relativity of simultaneity (80)Lorentz transformations (80)Time dilation and length contraction (81)Mass-energy equivalence (82)Relativistic energy-momentum relation (86)V ocabulary (89)正文标记说明：蓝色Arial字体（例如energy）：已知的专业词汇蓝色Arial字体加下划线（例如electromagnetism）：新学的专业词汇黑色Times New Roman字体加下划线（例如postulate）：新学的普通词汇1 Physics 物理学1 Physics 物理学Introduction to physicsPhysics is a part of natural philosophy and a natural science that involves the study of matter and its motion through space and time, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Over the last two millennia, physics was a part of natural philosophy along with chemistry, certain branches of mathematics, and biology, but during the Scientific Revolution in the 17th century, the natural sciences emerged as unique research programs in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry,and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms of other sciences, while opening new avenues of research in areas such as mathematics and philosophy.Physics also makes significant contributions through advances in new technologies that arise from theoretical breakthroughs. For example, advances in the understanding of electromagnetism or nuclear physics led directly to the development of new products which have dramatically transformed modern-day society, such as television, computers, domestic appliances, and nuclear weapons; advances in thermodynamics led to the development of industrialization; and advances in mechanics inspired the development of calculus.Core theoriesThough physics deals with a wide variety of systems, certain theories are used by all physicists. Each of these theories were experimentally tested numerous times and found correct as an approximation of nature (within a certain domain of validity).For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger than atoms and moving at much less than the speed of light. These theories continue to be areas of active research, and a remarkable aspect of classical mechanics known as chaos was discovered in the 20th century, three centuries after the original formulation of classical mechanics by Isaac Newton (1642–1727) 【艾萨克·牛顿】.University PhysicsThese central theories are important tools for research into more specialized topics, and any physicist, regardless of his or her specialization, is expected to be literate in them. These include classical mechanics, quantum mechanics, thermodynamics and statistical mechanics, electromagnetism, and special relativity.Classical and modern physicsClassical mechanicsClassical physics includes the traditional branches and topics that were recognized and well-developed before the beginning of the 20th century—classical mechanics, acoustics, optics, thermodynamics, and electromagnetism.Classical mechanics is concerned with bodies acted on by forces and bodies in motion and may be divided into statics (study of the forces on a body or bodies at rest), kinematics (study of motion without regard to its causes), and dynamics (study of motion and the forces that affect it); mechanics may also be divided into solid mechanics and fluid mechanics (known together as continuum mechanics), the latter including such branches as hydrostatics, hydrodynamics, aerodynamics, and pneumatics.Acoustics is the study of how sound is produced, controlled, transmitted and received. Important modern branches of acoustics include ultrasonics, the study of sound waves of very high frequency beyond the range of human hearing; bioacoustics the physics of animal calls and hearing, and electroacoustics, the manipulation of audible sound waves using electronics.Optics, the study of light, is concerned not only with visible light but also with infrared and ultraviolet radiation, which exhibit all of the phenomena of visible light except visibility, e.g., reflection, refraction, interference, diffraction, dispersion, and polarization of light.Heat is a form of energy, the internal energy possessed by the particles of which a substance is composed; thermodynamics deals with the relationships between heat and other forms of energy.Electricity and magnetism have been studied as a single branch of physics since the intimate connection between them was discovered in the early 19th century; an electric current gives rise to a magnetic field and a changing magnetic field induces an electric current. Electrostatics deals with electric charges at rest, electrodynamics with moving charges, and magnetostatics with magnetic poles at rest.Modern PhysicsClassical physics is generally concerned with matter and energy on the normal scale of1 Physics 物理学observation, while much of modern physics is concerned with the behavior of matter and energy under extreme conditions or on the very large or very small scale.For example, atomic and nuclear physics studies matter on the smallest scale at which chemical elements can be identified.The physics of elementary particles is on an even smaller scale, as it is concerned with the most basic units of matter; this branch of physics is also known as high-energy physics because of the extremely high energies necessary to produce many types of particles in large particle accelerators. On this scale, ordinary, commonsense notions of space, time, matter, and energy are no longer valid.The two chief theories of modern physics present a different picture of the concepts of space, time, and matter from that presented by classical physics.Quantum theory is concerned with the discrete, rather than continuous, nature of many phenomena at the atomic and subatomic level, and with the complementary aspects of particles and waves in the description of such phenomena.The theory of relativity is concerned with the description of phenomena that take place in a frame of reference that is in motion with respect to an observer; the special theory of relativity is concerned with relative uniform motion in a straight line and the general theory of relativity with accelerated motion and its connection with gravitation.Both quantum theory and the theory of relativity find applications in all areas of modern physics.Difference between classical and modern physicsWhile physics aims to discover universal laws, its theories lie in explicit domains of applicability. Loosely speaking, the laws of classical physics accurately describe systems whose important length scales are greater than the atomic scale and whose motions are much slower than the speed of light. Outside of this domain, observations do not match their predictions.Albert Einstein【阿尔伯特·爱因斯坦】contributed the framework of special relativity, which replaced notions of absolute time and space with space-time and allowed an accurate description of systems whose components have speeds approaching the speed of light.Max Planck【普朗克】, Erwin Schrödinger【薛定谔】, and others introduced quantum mechanics, a probabilistic notion of particles and interactions that allowed an accurate description of atomic and subatomic scales.Later, quantum field theory unified quantum mechanics and special relativity.General relativity allowed for a dynamical, curved space-time, with which highly massiveUniversity Physicssystems and the large-scale structure of the universe can be well-described. General relativity has not yet been unified with the other fundamental descriptions; several candidate theories of quantum gravity are being developed.Research fieldsContemporary research in physics can be broadly divided into condensed matter physics; atomic, molecular, and optical physics; particle physics; astrophysics; geophysics and biophysics. Some physics departments also support research in Physics education.Since the 20th century, the individual fields of physics have become increasingly specialized, and today most physicists work in a single field for their entire careers. "Universalists" such as Albert Einstein (1879–1955) and Lev Landau (1908–1968)【列夫·朗道】, who worked in multiple fields of physics, are now very rare.Condensed matter physicsCondensed matter physics is the field of physics that deals with the macroscopic physical properties of matter. In particular, it is concerned with the "condensed" phases that appear whenever the number of particles in a system is extremely large and the interactions between them are strong.The most familiar examples of condensed phases are solids and liquids, which arise from the bonding by way of the electromagnetic force between atoms. More exotic condensed phases include the super-fluid and the Bose–Einstein condensate found in certain atomic systems at very low temperature, the superconducting phase exhibited by conduction electrons in certain materials,and the ferromagnetic and antiferromagnetic phases of spins on atomic lattices.Condensed matter physics is by far the largest field of contemporary physics.Historically, condensed matter physics grew out of solid-state physics, which is now considered one of its main subfields. The term condensed matter physics was apparently coined by Philip Anderson when he renamed his research group—previously solid-state theory—in 1967. In 1978, the Division of Solid State Physics of the American Physical Society was renamed as the Division of Condensed Matter Physics.Condensed matter physics has a large overlap with chemistry, materials science, nanotechnology and engineering.Atomic, molecular and optical physicsAtomic, molecular, and optical physics (AMO) is the study of matter–matter and light–matter interactions on the scale of single atoms and molecules.1 Physics 物理学The three areas are grouped together because of their interrelationships, the similarity of methods used, and the commonality of the energy scales that are relevant. All three areas include both classical, semi-classical and quantum treatments; they can treat their subject from a microscopic view (in contrast to a macroscopic view).Atomic physics studies the electron shells of atoms. Current research focuses on activities in quantum control, cooling and trapping of atoms and ions, low-temperature collision dynamics and the effects of electron correlation on structure and dynamics. Atomic physics is influenced by the nucleus (see, e.g., hyperfine splitting), but intra-nuclear phenomena such as fission and fusion are considered part of high-energy physics.Molecular physics focuses on multi-atomic structures and their internal and external interactions with matter and light.Optical physics is distinct from optics in that it tends to focus not on the control of classical light fields by macroscopic objects, but on the fundamental properties of optical fields and their interactions with matter in the microscopic realm.High-energy physics (particle physics) and nuclear physicsParticle physics is the study of the elementary constituents of matter and energy, and the interactions between them.In addition, particle physicists design and develop the high energy accelerators,detectors, and computer programs necessary for this research. The field is also called "high-energy physics" because many elementary particles do not occur naturally, but are created only during high-energy collisions of other particles.Currently, the interactions of elementary particles and fields are described by the Standard Model.●The model accounts for the 12 known particles of matter (quarks and leptons) thatinteract via the strong, weak, and electromagnetic fundamental forces.●Dynamics are described in terms of matter particles exchanging gauge bosons (gluons,W and Z bosons, and photons, respectively).●The Standard Model also predicts a particle known as the Higgs boson. In July 2012CERN, the European laboratory for particle physics, announced the detection of a particle consistent with the Higgs boson.Nuclear Physics is the field of physics that studies the constituents and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those in nuclear medicine and magnetic resonance imaging, ion implantation in materials engineering, and radiocarbon dating in geology and archaeology.University PhysicsAstrophysics and Physical CosmologyAstrophysics and astronomy are the application of the theories and methods of physics to the study of stellar structure, stellar evolution, the origin of the solar system, and related problems of cosmology. Because astrophysics is a broad subject, astrophysicists typically apply many disciplines of physics, including mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.The discovery by Karl Jansky in 1931 that radio signals were emitted by celestial bodies initiated the science of radio astronomy. Most recently, the frontiers of astronomy have been expanded by space exploration. Perturbations and interference from the earth's atmosphere make space-based observations necessary for infrared, ultraviolet, gamma-ray, and X-ray astronomy.Physical cosmology is the study of the formation and evolution of the universe on its largest scales. Albert Einstein's theory of relativity plays a central role in all modern cosmological theories. In the early 20th century, Hubble's discovery that the universe was expanding, as shown by the Hubble diagram, prompted rival explanations known as the steady state universe and the Big Bang.The Big Bang was confirmed by the success of Big Bang nucleo-synthesis and the discovery of the cosmic microwave background in 1964. The Big Bang model rests on two theoretical pillars: Albert Einstein's general relativity and the cosmological principle (On a sufficiently large scale, the properties of the Universe are the same for all observers). Cosmologists have recently established the ΛCDM model (the standard model of Big Bang cosmology) of the evolution of the universe, which includes cosmic inflation, dark energy and dark matter.Current research frontiersIn condensed matter physics, an important unsolved theoretical problem is that of high-temperature superconductivity. Many condensed matter experiments are aiming to fabricate workable spintronics and quantum computers.In particle physics, the first pieces of experimental evidence for physics beyond the Standard Model have begun to appear. Foremost among these are indications that neutrinos have non-zero mass. These experimental results appear to have solved the long-standing solar neutrino problem, and the physics of massive neutrinos remains an area of active theoretical and experimental research. Particle accelerators have begun probing energy scales in the TeV range, in which experimentalists are hoping to find evidence for the super-symmetric particles, after discovery of the Higgs boson.Theoretical attempts to unify quantum mechanics and general relativity into a single theory1 Physics 物理学of quantum gravity, a program ongoing for over half a century, have not yet been decisively resolved. The current leading candidates are M-theory, superstring theory and loop quantum gravity.Many astronomical and cosmological phenomena have yet to be satisfactorily explained, including the existence of ultra-high energy cosmic rays, the baryon asymmetry, the acceleration of the universe and the anomalous rotation rates of galaxies.Although much progress has been made in high-energy, quantum, and astronomical physics, many everyday phenomena involving complexity, chaos, or turbulence are still poorly understood. Complex problems that seem like they could be solved by a clever application of dynamics and mechanics remain unsolved; examples include the formation of sand-piles, nodes in trickling water, the shape of water droplets, mechanisms of surface tension catastrophes, and self-sorting in shaken heterogeneous collections.These complex phenomena have received growing attention since the 1970s for several reasons, including the availability of modern mathematical methods and computers, which enabled complex systems to be modeled in new ways. Complex physics has become part of increasingly interdisciplinary research, as exemplified by the study of turbulence in aerodynamics and the observation of pattern formation in biological systems.Vocabulary★natural science 自然科学academic disciplines 学科astronomy 天文学in their own right 凭他们本身的实力intersects相交，交叉interdisciplinary交叉学科的，跨学科的★quantum 量子的theoretical breakthroughs 理论突破★electromagnetism 电磁学dramatically显著地★thermodynamics热力学★calculus微积分validity★classical mechanics 经典力学chaos 混沌literate 学者★quantum mechanics量子力学★thermodynamics and statistical mechanics热力学与统计物理★special relativity狭义相对论is concerned with 关注，讨论，考虑acoustics 声学★optics 光学statics静力学at rest 静息kinematics运动学★dynamics动力学ultrasonics超声学manipulation 操作，处理，使用University Physicsinfrared红外ultraviolet紫外radiation辐射reflection 反射refraction 折射★interference 干涉★diffraction 衍射dispersion散射★polarization 极化，偏振internal energy 内能Electricity电性Magnetism 磁性intimate 亲密的induces 诱导，感应scale尺度★elementary particles基本粒子★high-energy physics 高能物理particle accelerators 粒子加速器valid 有效的，正当的★discrete离散的continuous 连续的complementary 互补的★frame of reference 参照系★the special theory of relativity 狭义相对论★general theory of relativity 广义相对论gravitation 重力，万有引力explicit 详细的，清楚的★quantum field theory 量子场论★condensed matter physics凝聚态物理astrophysics天体物理geophysics地球物理Universalist博学多才者★Macroscopic宏观Exotic奇异的★Superconducting 超导Ferromagnetic铁磁质Antiferromagnetic 反铁磁质★Spin自旋Lattice 晶格，点阵，网格★Society社会，学会★microscopic微观的hyperfine splitting超精细分裂fission分裂，裂变fusion熔合，聚变constituents成分，组分accelerators加速器detectors 检测器★quarks夸克lepton 轻子gauge bosons规范玻色子gluons胶子★Higgs boson希格斯玻色子CERN欧洲核子研究中心★Magnetic Resonance Imaging磁共振成像，核磁共振ion implantation 离子注入radiocarbon dating放射性碳年代测定法geology地质学archaeology考古学stellar 恒星cosmology宇宙论celestial bodies 天体Hubble diagram 哈勃图Rival竞争的★Big Bang大爆炸nucleo-synthesis核聚合，核合成pillar支柱cosmological principle宇宙学原理ΛCDM modelΛ-冷暗物质模型cosmic inflation宇宙膨胀1 Physics 物理学fabricate制造，建造spintronics自旋电子元件，自旋电子学★neutrinos 中微子superstring 超弦baryon重子turbulence湍流，扰动，骚动catastrophes突变，灾变，灾难heterogeneous collections异质性集合pattern formation模式形成University Physics2 Classical mechanics 经典力学IntroductionIn physics, classical mechanics is one of the two major sub-fields of mechanics, which is concerned with the set of physical laws describing the motion of bodies under the action of a system of forces. The study of the motion of bodies is an ancient one, making classical mechanics one of the oldest and largest subjects in science, engineering and technology.Classical mechanics describes the motion of macroscopic objects, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars, and galaxies. Besides this, many specializations within the subject deal with gases, liquids, solids, and other specific sub-topics.Classical mechanics provides extremely accurate results as long as the domain of study is restricted to large objects and the speeds involved do not approach the speed of light. When the objects being dealt with become sufficiently small, it becomes necessary to introduce the other major sub-field of mechanics, quantum mechanics, which reconciles the macroscopic laws of physics with the atomic nature of matter and handles the wave–particle duality of atoms and molecules. In the case of high velocity objects approaching the speed of light, classical mechanics is enhanced by special relativity. General relativity unifies special relativity with Newton's law of universal gravitation, allowing physicists to handle gravitation at a deeper level.The initial stage in the development of classical mechanics is often referred to as Newtonian mechanics, and is associated with the physical concepts employed by and the mathematical methods invented by Newton himself, in parallel with Leibniz【莱布尼兹】, and others.Later, more abstract and general methods were developed, leading to reformulations of classical mechanics known as Lagrangian mechanics and Hamiltonian mechanics. These advances were largely made in the 18th and 19th centuries, and they extend substantially beyond Newton's work, particularly through their use of analytical mechanics. Ultimately, the mathematics developed for these were central to the creation of quantum mechanics.Description of classical mechanicsThe following introduces the basic concepts of classical mechanics. For simplicity, it often2 Classical mechanics 经典力学models real-world objects as point particles, objects with negligible size. The motion of a point particle is characterized by a small number of parameters: its position, mass, and the forces applied to it.In reality, the kind of objects that classical mechanics can describe always have a non-zero size. (The physics of very small particles, such as the electron, is more accurately described by quantum mechanics). Objects with non-zero size have more complicated behavior than hypothetical point particles, because of the additional degrees of freedom—for example, a baseball can spin while it is moving. However, the results for point particles can be used to study such objects by treating them as composite objects, made up of a large number of interacting point particles. The center of mass of a composite object behaves like a point particle.Classical mechanics uses common-sense notions of how matter and forces exist and interact. It assumes that matter and energy have definite, knowable attributes such as where an object is in space and its speed. It also assumes that objects may be directly influenced only by their immediate surroundings, known as the principle of locality.In quantum mechanics objects may have unknowable position or velocity, or instantaneously interact with other objects at a distance.Position and its derivativesThe position of a point particle is defined with respect to an arbitrary fixed reference point, O, in space, usually accompanied by a coordinate system, with the reference point located at the origin of the coordinate system. It is defined as the vector r from O to the particle.In general, the point particle need not be stationary relative to O, so r is a function of t, the time elapsed since an arbitrary initial time.In pre-Einstein relativity (known as Galilean relativity), time is considered an absolute, i.e., the time interval between any given pair of events is the same for all observers. In addition to relying on absolute time, classical mechanics assumes Euclidean geometry for the structure of space.Velocity and speedThe velocity, or the rate of change of position with time, is defined as the derivative of the position with respect to time. In classical mechanics, velocities are directly additive and subtractive as vector quantities; they must be dealt with using vector analysis.When both objects are moving in the same direction, the difference can be given in terms of speed only by ignoring direction.University PhysicsAccelerationThe acceleration , or rate of change of velocity, is the derivative of the velocity with respect to time (the second derivative of the position with respect to time).Acceleration can arise from a change with time of the magnitude of the velocity or of the direction of the velocity or both . If only the magnitude v of the velocity decreases, this is sometimes referred to as deceleration , but generally any change in the velocity with time, including deceleration, is simply referred to as acceleration.Inertial frames of referenceWhile the position and velocity and acceleration of a particle can be referred to any observer in any state of motion, classical mechanics assumes the existence of a special family of reference frames in terms of which the mechanical laws of nature take a comparatively simple form. These special reference frames are called inertial frames .An inertial frame is such that when an object without any force interactions (an idealized situation) is viewed from it, it appears either to be at rest or in a state of uniform motion in a straight line. This is the fundamental definition of an inertial frame. They are characterized by the requirement that all forces entering the observer's physical laws originate in identifiable sources (charges, gravitational bodies, and so forth).A non-inertial reference frame is one accelerating with respect to an inertial one, and in such a non-inertial frame a particle is subject to acceleration by fictitious forces that enter the equations of motion solely as a result of its accelerated motion, and do not originate in identifiable sources. These fictitious forces are in addition to the real forces recognized in an inertial frame.A key concept of inertial frames is the method for identifying them. For practical purposes, reference frames that are un-accelerated with respect to the distant stars are regarded as good approximations to inertial frames.Forces; Newton's second lawNewton was the first to mathematically express the relationship between force and momentum . Some physicists interpret Newton's second law of motion as a definition of force and mass, while others consider it a fundamental postulate, a law of nature. Either interpretation has the same mathematical consequences, historically known as "Newton's Second Law":a m t v m t p F ===d )(d d dThe quantity m v is called the (canonical ) momentum . The net force on a particle is thus equal to rate of change of momentum of the particle with time.So long as the force acting on a particle is known, Newton's second law is sufficient to。