Chapter 6 electromechanics

大学物理-电磁学（英文授课）IntroductionElectromagnetism is a field of physics that concerns itself with the study of electromagnetic forces and fields. It is a branch of physics that focuses on the interaction between electrically charged particles, including charged particles at rest and moving charges. This course is designed to help students understand the basic principles of electromagnetism, including electric and magnetic fields, electromagnetic radiation, and electromagnetic waves.Electric FieldsElectric fields are created by electric charges, which are either positive or negative. The electric field is said to be the space surrounding a charged particle. If another charged particle is placed in the electric field, it will experience a force. The direction of the force depends on the charge of the particle and the direction of the electric field.Magnetic FieldsMagnetic fields are created by moving charges. A magnetic field is said to be the space surrounding a magnetic object. If a charged particle is placed in a magnetic field, it will move in a circular path. The direction of the circular path depends on the charge of the particle and the direction of the magnetic field. Electromagnetic FieldsAn electromagnetic field is created by the interaction of an electric field and a magnetic field. Electromagnetic fields have both electric and magnetic components, and they travel through space at the speed of light. Electromagnetic waves are a form of electromagnetic radiation that carries energy. Electromagnetic radiation includes radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays.Maxwell's EquationsMaxwell's equations describe the behavior of electric and magnetic fields. They are a set of partial differential equations that relate the electric and magnetic fields to the electric charges and currents that are present. The equations describe how an electric field can produce a magnetic field, and a magnetic field can produce an electric field. They also describe how the electromagnetic fields propagate through space.Electromagnetic WavesElectromagnetic waves are waves of energy that are propagated through space by the interaction of electric and magnetic fields. Electromagnetic waves do not require any medium to propagate through. They can travel through a vacuum, which is why they are also known as vacuum waves.Electromagnetic waves are classified based on their frequency and wavelength. Radio waves have the lowest frequency, and gamma rays have the highest frequency. Radio waves have the longest wavelength, and gamma rays have the shortest wavelength.Applications of ElectromagnetismElectromagnetism has many practical applications in our daily lives. Some of the most common applications include electric motors, generators, transformers, telecommunication devices, medical imaging devices, and microwave ovens. Electromagnetism has also played a significant role in the development of modern technology, including computers, television, radio, and mobile phones.ConclusionElectromagnetism is a fascinating field of physics that has wide-ranging applications in our daily lives. This course provides students with a comprehensive understanding of electric and magnetic fields, electromagnetic radiation, and electromagnetic waves. By studying electromagnetism, students can gain a deeper appreciation for the fundamental principles that govern the behavior of the universe around us.Electromagnetism is one of the four fundamental forces of nature, along with gravity, strong nuclear force, and weak nuclear force. It is a field of physics with numerous applications in our modern society. Without the understanding of electromagnetism, we would not have the modern comforts that we have today, including electricity, the internet, cell phones, and many other devices.One of the most significant contributions of electromagnetism to modern society is the use of electric motors. Electric motors are devices that convert electrical energy into mechanical energy.They are used in a wide range of applications, from household appliances to transportation systems. The underlying principle of electric motors is electromagnetic induction, which is the process of inducing an electric current in a conductor by varying the magnetic field around it.Another important application of electromagnetism is in generators. Generators are devices that convert mechanical energy into electrical energy. They are often used in power plants to generate electricity that is distributed to homes and businesses. The principle of electromagnetic induction is also used in generators. When a conductor moves through a magnetic field, an electric current is induced in the conductor.Electromagnetism also plays a central role in the functioning of transformers. A transformer is a device that changes the voltage of an alternating current (AC) power supply. Transformers are used to step up or step down the voltage of an AC power supply. They are used in power grids to maintain a constant voltage throughout the grid. The principle used in transformers is electromagnetic induction, with the primary and secondary coils of wire interacting with the magnetic field to produce the desired voltage change. Telecommunication devices, including radios, televisions, and cell phones, also rely on the principles of electromagnetism. The radio waves used for communication are a form of electromagnetic radiation. Radio waves are used to transmit and receive signals between devices. The workings of these devices depend on the principles of electromagnetic induction and electromagnetic radiation.In addition to powering devices, electromagnetism is used in medical imaging devices. Magnetic resonance imaging (MRI) machines use magnetic fields and radio waves to produce images of the body's internal structures. The patient is placed in a powerful magnetic field, which causes the protons in their body to align with the field. A radio wave is then sent through the body, causing the protons to produce a signal. The signal is detected, and an image is produced based on the strength and location of the signal.Microwave ovens are another example of electromagnetism in action. These appliances use microwaves to cook food. Microwaves are a type of electromagnetic radiation with a frequency of around 2.4 GHz. The microwaves cause the water molecules in the food to vibrate rapidly, producing heat. This heats the food quickly and evenly, making it a popular method for cooking.The study of electromagnetism has also led to the development of modern technology. Computers, televisions, radios, and cell phones all rely on the principles of electromagnetism. The development of these technologies has revolutionized the way we live and communicate. The internet, for example, would not exist without the principles of electromagnetism.In conclusion, electromagnetism is a fascinating field of physics with numerous practical applications in our daily lives. It is the foundation of modern technology, and our society would not be the same without it. By studying electromagnetism, we can gain a deeper understanding of the world around us and appreciate thefundamental principles that govern our universe. As technology advances, we can expect even more exciting and innovative applications of electromagnetism in the years to come.。

半导体物理器件与工艺英文原版Semiconductor Physics, Devices, and Fabrication.Introduction.Semiconductors are materials with electricalconductivity between that of conductors and insulators.This unique property makes them essential for a wide rangeof electronic devices, including transistors, diodes, and solar cells.Semiconductor Physics.The electrical properties of semiconductors are determined by their electronic band structure. In an insulator, the valence band (the band of electrons that are tightly bound to the atoms) is filled, and the conduction band (the band of electrons that are free to move) is empty. In a conductor, the conduction band is partially filled. In a semiconductor, the conduction band is empty and thevalence band is filled, but there is a small energy gap between the two bands.When a semiconductor is exposed to light or heat, electrons can be excited from the valence band to the conduction band. These electrons are then free to move, and the semiconductor becomes more conductive. This phenomenon is known as intrinsic conduction.Semiconductors can also be doped with impurities to increase their conductivity. Donor impurities add electrons to the semiconductor, while acceptor impurities remove electrons. Doped semiconductors are used to create transistors, diodes, and other electronic devices.Semiconductor Devices.Transistors are the basic building blocks of electronic circuits. They can be used to amplify signals, switch currents, and store data. Transistors are made from three layers of semiconductor material: the emitter, the base, and the collector.Diodes are another important type of semiconductor device. They allow current to flow in one direction but not the other. Diodes are used in a variety of applications, including rectifying AC currents and protecting circuits from overvoltage.Solar cells are semiconductor devices that convertlight into electricity. Solar cells are made from photovoltaic materials, which are materials that generate an electrical current when exposed to light. Solar cells are used to power a variety of devices, including calculators, watches, and satellites.Semiconductor Fabrication.Semiconductors are fabricated using a variety of processes, including lithography, etching, and deposition.Lithography is the process of creating patterns in semiconductor materials. Lithography is used to create the features of transistors, diodes, and other electronicdevices.Etching is the process of removing material from semiconductor wafers. Etching is used to create the trenches and vias that connect the different layers of a semiconductor device.Deposition is the process of adding material to semiconductor wafers. Deposition is used to create the metal layers that connect the different parts of a semiconductor device.Semiconductor fabrication is a complex and precise process. The quality of the final product depends on the accuracy of each step in the fabrication process.Conclusion.Semiconductors are essential for a wide range of electronic devices. The physics of semiconductors and the processes used to fabricate semiconductor devices are complex and challenging, but they are also essential forthe development of new and innovative electronic technologies.。

电化学原理第一章习题答案1、解：2266KCl KCl H O H O 0.001141.31.010142.31010001000c K K K K cm 11λ−−−−×=+=+=+×=×Ω溶液 2、解：E V Fi i =λ，FE V i i λ=，，， 10288.0−⋅=+s cm V H 10050.0−⋅=+s cm V K 10051.0−⋅=−s cm V Cl 3、解：,62.550121,,,,2−−⋅Ω=−+=eq cm KCl o HCl o KOH o O H o λλλλ2O c c c ,c 1.004H H +−====设故，2,811c5.510cm 1000o H O λκ−−−==×Ω4、（1）121,,Cl ,t t 1,t 76.33mol (KCl o KCl o Cl cm λλλλλ−−−−+−+−=++=∴==Ω⋅∵中）121121121,K ,Na ,Cl 73.49mol 50.14mol 76.31mol (NaCl o o o cm cm cm λλλ++−−−−−−−=Ω⋅=Ω⋅=Ω⋅同理：，，中）（2）由上述结果可知： 121Cl ,Na ,121Cl ,K ,mol 45.126mol 82.142−−−−⋅Ω=+⋅Ω=+−+−+cm cm o o o o λλλλ，在KCl 与NaCl 溶液中−Cl ,o λ相等，所以证明离子独立移动定律的正确性；（3） vs cm vs cm u vs cm u F u a o o l o l o i o /1020.5,/1062.7,/1091.7,/24N ,24K ,24C ,C ,,−−−×=×=×==++−−λλ5、解：Cu(OH)2== Cu 2++2OH -,设=y ；2Cu c +OH c −=2y 则K S =4y 3因为u=Σu i =KH 2O+10-3[y λCu 2++2y λOH -]以o λ代替λ（稀溶液）代入上式，求得y=1.36×10-4mol/dm 3所以Ks=4y 3=1.006×10-11 (mol/dm 3)36、解： ==+，令=y ，3AgIO +Ag −3IO Ag c +3IO c −=y ，则=y S K 2，K=i K ∑=+（y O H K 2310−+Ag λ+y −3IO λ）作为无限稀溶液处理，用0λ代替，=+y O H K 2310−3AgIO λ则：y=43651074.1104.68101.11030.1−−−×=××−×L mol /;∴= y S K 2=3.03810−×2)/(L mol 7、解：HAc o ,λ=HCl o ,λ+NaAc o ,λ-NaCl o ,λ=390.7，121−−⋅Ωeq cm HAc o ,λ=9.02121−−⋅Ωeq cm ∴α0/λλ==0.023，==1.69αK _2)1/(V αα−510−×8、解：由欧姆定律IR=iS KS l ⋅=K il,∵K=1000c λ,∴IR=1000il cλ⋅=V 79.05.0126101010533≈××××− 9、解：公式log ±γ=-0.5115||||+Z −Z I （设25）C °（1）±γ=0.9740，I=212i i z m ∑,I=212i i c z ∑，=（）±m ++νm −−νm ν1（2）±γ=0.9101，（3）±γ=0.6487，（4）±γ=0.811410、解：=+H a ±γ+H m ，pH=-log =-log （0.209+H a 4.0×）=1.08电化学原理第二章习题答案1、 解：()+2326623Sb O H e Sb H O ++++ ，()−236H H +6e + ，电池:2322323Sb O H Sb H O ++解法一：00G E nF ∆=−83646F =0.0143V ≈，E=+0E 2.36RT F 2232323log H Sb O Sb H OP a a a ==0.0143V0E 解法二：0602.3 2.3log log 6Sb Sb H H RT RT a a F Fϕϕϕ+++=+=+； 2.3log H RTa Fϕ+−=∴000.0143Sb E E ϕϕϕ+−=−===V2解：⑴，(()+22442H O e H O +++ )−224H H +4e + ；电池:22222H O H O +2220022.3log 4H O H O P P RT E E E Fa =+= 查表：0ϕ+=1.229V ，0ϕ−=0.000V ，001.229E V ϕϕ+−∴=−= ⑵视为无限稀释溶液，以浓度代替活度计算()242Sn Sn e ++−+ ，()，电池:32222Fe e Fe ++++ 23422Sn Fe Sn Fe 2+++++ +23422022.3log 2Sn Fe Sn Fe C C RT E E F C C ++++=+=（0.771-0.15）+220.05910.001(0.01)log 20.01(0.001)××=0.6505V ⑶()，，(0.1)Ag Ag m e +−+ ()(1)Ag m e Ag +++ (1)(0.1)Ag m Ag m ++→电池：(1)0(0.1)2.3log Ag m Ag m a RT E E F a ++=+，（其中，=0） 0E 查表：1m 中3AgNO 0.4V γ±=，0.1m 中3AgNO 0.72V γ±=， 2.310.4log0.0440.10.72RT E V F×∴==× 3、 解：2222|(),()|(),Cl Hg Hg Cl s KCl m Cl P Pt ()2222Hg Cl Hg Cl e −−++ ，()222Cl e Cl −++ ，222Hg Cl Hg Cl 2+ 电池：222200002.3log 2Cl Hg Hg Cl P a RT E E E F a ϕϕ+−=+==−∵O 1.35950.2681 1.0914(25C)E V ，∴=−=设 由于E 与无关，故两种溶液中的电动势均为上值Cl a −其他解法：①E ϕϕ+=−−0，亦得出0E ϕϕ+=−−②按Cl a −计算ϕ+，查表得ϕ甘汞，则E ϕϕ+=−甘汞 4、 ⑴解法一：23,(1)|(1)()H Pt H atm HCl a AgNO m Ag +=()222H H e +−+ 222，()Ag e Ag +++ g ，2222H Ag H A ++++ 电池：有E ϕϕϕ+−=−=+，02.3log()AgAgAg RTE m Fϕγ++±∴=−。

中文版Ｅｘplｏring-Chemisｔry-ｗiｔh－Electronｉｃ-Structuｒｅ-Mｅｔhos－————————————————————————————————作者：————————————————————————————————日期:Expｌoring Chｅmｉstry with EleｃtroｎiｃStruｃture ＭｅｔｈｏdSecｏｎd EｄithionJaｍeｓB．FｏｒｅｓｍanAｅleenＦｒischGaussｉａｎ,IncPittｓburgh,ＰA2002年９月25日特别声明本文转自南开大学BＢS网站,在此对译者表示衷心感谢!!!！用Gａusｓian研究化学问题说明接触Gaｕssian已经很久了,但真正用Ｇaussｉan做东西还是临近博士毕业时的事情。

当时做计算的时候,就特别希望有一本具体怎么使用从头算的书，可惜一直没有找到。

来到这里后,在新买的Gauｓsｉan９8包中发现了这本书，感觉如获至宝，也希望能够提供给想用Gaus ｓｉan做东西的朋友。

我不是专门做量化的，很多术语不清楚怎么翻译,手头又没有中文的资料,错误的地方，只能希望内行来指点了。

其实这本书里面介绍的东西,不止限于Ｇaｕssian程序的。

对于从事从头算研究的都有帮助。

内容中有很多计算实例,都是在Gauｓsｉａｎ94,98程序中提供的。

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Ｆoｒeｓmａｎ,ElｅｅｎＦrisｃh出版社Gaｕｓsiａn,Iｎc,ＵSA,1９96目录特别声明ﻩ错误!未定义书签。

用Gaｕｓsiａｎ研究化学问题........................................................................ 错误!未定义书签。

说明ﻩ错误!未定义书签。

电动力学是物理学中非常重要的分支之一，它研究电荷和电荷所产生的电场之间的相互作用。

而《电动力学导论格里菲斯中文版》是由美国加州大学河滨分校的大卫·J·格里菲斯所撰写的一本电动力学经典教材，其中第五章主要讨论的是磁场的静止情况和运动情况。

1. 静磁场第五章开篇即介绍了静磁场的基本概念和性质。

在这一部分中，格里菲斯首先介绍了磁场的产生原理，即电流产生磁场的安培定律。

通过对安培定律的深入探讨，读者可以逐步理解磁场的强弱和方向是如何受电流产生的影响的。

在阐述完安培定律后，格里菲斯进一步引入了磁场的高斯定律和比奥-萨伐特定律，这两个定律分别用于描述磁场的闭合性和洛伦兹力的作用。

2. 磁场的变化第五章的第二部分涉及到磁场的变化情况。

讨论了磁感应线圈、法拉第电磁感应定律和自感等内容。

这部分内容探讨了磁场与时间的关系，解释了磁场变化对于感生电动势和感生电流的影响，为后续章节的讨论奠定了基础。

3. 资料分析和补充第五章的第三部分主要是对前两部分内容的回顾和总结。

并结合实际例子来对磁场的理论知识进行应用和延伸，使读者能够更加直观生动地理解磁场的作用和应用。

总结通过对《电动力学导论格里菲斯中文版》第五章的深入阐述和梳理，不仅加深了我对静磁场和磁场变化的理解，同时也为我在电动力学领域的学习和研究提供了丰富的知识储备。

在学习过程中，我也意识到电动力学作为物理学中的重要分支，其理论知识和实际应用都具有广泛的价值和意义。

希望通过对电动力学的学习和探索，能够在相关领域取得更多的成果，并为科学研究和技术创新做出自己的贡献。

第五章的内容涵盖了静磁场和磁场的变化，这些内容是电动力学中非常重要的组成部分。

在这一部分中，格里菲斯详细地介绍了静磁场的基本概念和性质，包括安培定律、高斯定律和比奥-萨伐特定律。

通过对这些定律的深入探讨，读者可以更加深入地理解磁场与电流之间的关系，以及磁场的闭合性和洛伦兹力的作用。

在第二部分中，磁场的变化成为焦点，涉及到磁感应线圈、法拉第电磁感应定律和自感等内容。

The Challenge:Using a Customized Waveform to Mimic theHuman Cartilage Mechanical EnvironmentBackgroundApproximately 40 million Americans suffer from localized damage to the cartilage and subchondral bone. This leads to pain, loss of joint function and osteoarthritis. There is a pervasive need for effective clinical treatments to repair cartilage injuries.Regenerative medicine approaches are currently investigated through the replacement of the damaged cartilage with tissue-engineered cartilage constructs. Porous scaffolds not only provide a boundary for retention of cells, but also act as a substrate to which the anchorage-dependent chondrocytes can adhere.It is known that mechanical modulation has a significant impact on cell differentiation and proliferation. Thus,applying accurate and efficient mechanical stimuli is crucial in quality control of the tissue product. This may also in turn guide diagnosis and future therapy improvement. In this study, the Bose ® ElectroForce ® 5500 test instrument (Figure 1) was used to impose a customized waveform on a hydrogel, and the changes in sample properties were monitored over time.Sinusoidal cyclic waveforms are typically used when studying relationships between cell growth and mechanical stimulation; however, there is limitedinformation on using customized waveforms. It would be beneficial to use a waveform that mimics the mechanical environment of a human knee joint while walking during the in vitro tissue-engineered cartilage development.Polyethylene glycol (PEG) hydrogel sheets (4” x 4”) were purchased from MedlineIndustries. Hydrogel specimens, punched from the hydrogel sheet, were 12 mm in diameter and 6 mm in height (Figure 2).The ElectroForce 5500 systemhas a maximum force capacityof 200 N and a maximumdisplacement of 13 mm. The system was equipped with a 200 N load cell and a pair of 25 mm diameter platens. A preloading force of 0.1 N was used to ensure that the entire scaffold surface was in contact with the compression platens prior to testing (Figure 3).External waveform is a feature of the WinTest software that offers users with the ability to run custom waveforms whenmore complex mechanicalanalysis is required. Externalwaveform allows the importation of point by point files whichdefine evenly spaced data points as a function of time.Meeting the ChallengeThe ElectroForce 5500 test instrument, in combination with WinTest ® software, is ideal for mechanical studies in biomedical research. It provides precise force and displacement control throughout the experiment. Customized waveforms can be realized by externallyimporting them into the WinTest software at which point they can be reproduced by the patented Bose linearactuator that features a frictionless moving-magnet design.Materials and MethodsFigure 2 - Hydrogel Specimen Figure 1 - Bose ® ElectroForce ®5500 Test InstrumentFigure 3 - Specimen Loaded Between Compression PlatensBose Corporation – ElectroForce Systems Group10250 Valley View Road, Suite 113, Eden Prairie, Minnesota 55344 USA Email:*********************–Website: Phone: 952-278-3070 – Fax: 952-278-3071©2014 Bose Corporation. Patent rights issued and/or pending in the United States and other countries. Bose, the Bose logo, ElectroForce and WinT est are registered trademarks of Bose Corporation. 063014In order to create a WinTest ® software readable point by point file, the following steps were used:The waveform was extracted and replotted in Excel.According to normal human walking speed of 5 km/h, a one gait cycle time of 1.1 sec was obtained and used as a new X axis (Figure 5).An ASCII file was constructed by the text editor. The Y axis strain points were scaled according to the specimenthickness and used for the ASCII file. The above waveform contained 1100 points, so the time interval between points was set to 0.001 sec to match with the gait cycle time.Each pass through the waveform = 1100 x 0.001 = 1.1 sec. The ASCII file was imported into WinTest software. A point by point file was exported and used for the test setup.The same external waveform was successfully applied to all the specimens (Figure 6). Similar testing results of three specimens were achieved and reliable repeatability of this testing method was demonstrated (Displacement difference between samples: <2.5%; Load difference between samples:<13.9%). Compared to the original extracted waveform in the ASCII file, the majority of the waveform details were retained accurately.The Bose ® ElectroForce ® 5500 test instrument is a powerful tool, which is not only capable of generating sinusoidal, triangle, square, ramp and block waveforms, but also excels in precise waveform customization. Combined with easy to use WinTest software, the ElectroForce 5500 testinstrument is able to deliver waveform profiles that fit the needs of a particular experiment and gives researchers the ability to implement their ideas.SummaryFigure 4 - Strain at the Contact of Joint Cartilage during the Gait Cycle (Halonen et al., 2013)A waveform model (Figure 4, pink line) of strain vs. gait cycle based on simulation of human walking was used inthis study (Halonen, et al., 2013).Figure 5 - Extracted WaveformResultsThree specimens were tested with the externalwaveform, and displacement and load data were tracked during the test.(1) Halonen, K.S., M. E. Mononen, J. S. Jurvelin, J. Töyräs, and R.K. Korhonen. “Importance of depth-wise distibution of collagen and proteoglycans in articular cartilage - a 3D finite elment study of stresses and strains in the human knee joint.” Journal of Biomechanics (2013).ReferenceFigure 6 - Average Result of Three Specimens。

Electrochemical ThermodynamicsSolid/Solid，Solid/Liquid，Liquid-Liquid junction (contact) potentialMembrane potentialConcentration CellsEnrico Fermi （1901－1954）FermiLevelFermi received the NobelPrize in 1938 for "hisdiscovery of new radioactiveelements produced byneutron irradiation, and forthe discovery of nuclearreactions brought about byslow neutrons."Fermi Levelthe top of the collection of electron energy levelsat absolute zero temperatureE=0 (vacuum level)E F (Fermi level)Fermi Energy: minimum energy to remove electron from metal ----( work function ---work of escaping electron)Metal 1Metal 2CBVBE n e r g yHClHClH+Cl +a 2 < a 1AgNO 3HNO 3Ag+H+a 2 = a 1Liquid / liquid junction potential(diffusion potential)21/l l φΔLiquid junction potential by different concentration of a singlebinary salt solution:21)()(lnz +-(z + -z -)t +i i a a F RT z + z -=l ΔΦ21)()(ln )(i i a a F RT t t −+−=for a single electrolyte of I-I valence:Salt BridgeA Role of Salt BridgesaturatedKClsolution(2)solution(1)Cl-K+Cl-K+ΔΦl(1)ΔΦ(2)Salt bridgejunction potential decreases to about 1 mV!(KNO3 , NH4NO3)KCl KCl Cl K l C C F RT t t 桥'ln )(1)1(−−=+φΔ'ln )(2)2(KCl KCl Cl K l C C F RT t t 桥−−=+φΔ)2()1(l l l φΔφΔφΔ+=''ln )(21KCl KCl Cl K C C t t −+−=21,C C C KCl >>QMembrane Potential M +(β)M +(α)electrolyte(β)electrolyte(α))()(βμαμ++=M M )()()()(βϕβμαϕαμF F M M +=+++Semi-permeable MembraneEm = g'K (-96 mV) + g'Na (+50 mV) + g'Ca (+134 mV) + g'Cl (-90 mV)E Na = -61 log [Na+]i / [Na+]o = +50 mVEm depends on the sum of the individual equilibrium potentials times the relative membrane conductance of each ionic species. g’K+ is much larger.Em = g‘K ＋E K ＋+ g’Na ＋E Na + g'Ca 2+E Ca + g'Cl -E ClE K = -61 log [K+]i / [K+]o = -96 mVMembrane PotentialsEnergy transduction by membrane proteins. The Na+-K+ATPase converts the free energy of phosphoryl transfer into the free energy of a Na+ion gradient. The ion gradient can then be used to pump materials into the cell, through the action of a secondary transporter such as the Na+-glucose sysmporter.R’Concentration CellA galvanic cell in which the chemical energy converted into electric energy is arisen from the concentration difference of the same species at the two electrodes of the cellThe electromotive force E comes from the change of Gibbs free energy ΔG that due to transport of mass from high concentration to low concentration.1.Electrode ConcentrationDifference Cell(-)Pt, H 2(p 1) | HCl(a ) | H 2(p 2), Pt (+)(-)K-Hg(a 1) | KNO 3(a ) | K-Hg(a 2) (+)P1P2Pt wire Pt wirebubblingCoating Pt black electrodeGas Electrode Concentration CellH2(p1) -2e-→2H+(a) 2H+(a) + 2e-→H2(p2)Positive electrode (cathode):reduction reaction 2H +(a ) + 2e -→H 2(p 2)Overall Consequence : H 2(p 1) →H 2(p 2)Negative electrode (anode):oxidation reaction:H 2(p 1) -2e -→2H +(a ) (-)Pt, H 2(p 1) | HCl(a ) | H 2(p 2), Pt (+)Result: transfer from high pressure to low pressure o o12ϕϕ=12ln P P zF RT E −=P 1 P 2Cu-Hg(x1=0.1)|CuSO4(a)|Cu-Hg(x2=0.01)(-) Cu-Hg(x1=0.1) →Cu2+(a+) + Hg+2e-(+) Cu2+(a+) + Hg + 2e-→Cu-Hg(x2=0.01)The cell overall reaction: Cu-Hg(x1= 0.1) →Cu-Hg(x2= 0.01)(-) Pt,Cl 2(p 1)| KCl(a ) |Cl 2(p 2),Pt (+)21ln P P zF RT E −=Net result of mass transport: high pressure to low one,High concentration to low one.12ln P P zF RT E −=(-)Pt, H 2(p 1) | HCl(a ) | H 2(p 2), Pt (+)2. Electrolyte ConcentrationDifference Cell(-)Ag|AgNO3(a1)||AgNO3(a2)|Ag (+)(+) Ag+(0.2 mol⋅kg-1) + e→Ag (-)Ag →Ag+(0.1 mol⋅kg-1) +e Ag+(0.2 mol⋅kg-1) →Ag+(0.1 mol⋅kg-1)→Ag,AgCl(s )|HCl(a 1)||HCl(a 2)|AgCl(s ),Ag→(-)Ag|AgNO 3(a 1)||AgNO 3(a 2)|Ag (+)2,1,ln ++−=Ag Ag a a F RTEPotential is caused by physical process apparently However, the mass transport is carried out indirectly by electrode reaction.=o EWhat we have learnt from this part?1.No matter the decrease of ΔG occurs caused by physical or chemical processes, it can give rise to cell electromotive force.2.The output energy of concentration cell is normally very small.Application of measurement ofelectromotive force KpM pH t a S H G E i r r r ,,,,,,,±±ΔΔΔ→γL L1Pt|F2(p Ө), F-2Pt|Cl2(pӨ), Cl-3Pt|O2(pӨ), H+ 4Cu2+|Cu5Pt|H2(pӨ), H+ 6Zn2+|Zn7Al3+|Al8Mg2+|Mg9Li+|Li ϕ--log a diagram -2-1-3Chemical reaction Two differenthalf cells (A lot of expts. required)(Well selected)Electrochemical thermodynamicsElectrode KineticsElectrochemistry is over 200 Years Old!Luigi Galvani–“Animal Electricity”(1791)Alesandro Volta –“Metallic Electricity”(1800) Hermann Nernst-Nernst Equation (1889) Alexander N. Frumkin-Electrode Kinetics (1930’s)A.N. Frumkin(1895-1976)Electrode Kinetics?The electrode process rate was related for the first time to the structure of the electrode-solution interface, heralding the birth of a new direction of electrochemistry –kinetics of the elementary act of electron transfer, the central problem of the kinetics ofelectrode processes.A.N Frumkin(1895-1976)A.N. Frumkin, Z. Physik. Chem., 1933, 164, 121.Characteristics of Electrode Kinetics Characteristics of Electrode Kinetics How to control the electrochemical process Accelerate or slow down the electrochemical reaction ( current !)How to control the electrochemical process Accelerate or slow down the electrochemical reaction ( current !)三电极体系Ox + ze Red(single electrode reaction)k 1k -1How to study the reaction rate in a electrolytic cell?1.Electrolyte solution2.Electrode materials and metal leads3.Electrode/liquid interfacessolid/solid interfaces --Electrode Kinetics Charge transfer and mass transportationMeasurement of decomposition potential (V)and currentdVd(Pt) Vd = 1.67 V (Hg)Vd= 3.5 VProducing 1 cm3H2onan area of 1 cm2 Hgwill take 500,000 yearswhen V is 1.23 VChange the cathode materials from Hg to Pt will accelerate the reaction rate significantly1.673.51.23Pt or Pt/C electrodeHg electrodeV d = E r + ΔE irVPolarizationV = E r + ΔEirOverpotential -η(1899)V= E r + ΔE ir> 0 ηΔEirΔE ir= ηanode+ ηcathode = ηa + ηc。