东南大学《954电路(电气工程)》考研真题与详解

954《电路（电气工程）》~2016年‎启用时间：2016-06-17全日制硕士‎研究生入学‎954《电路（电气工程）》课程复习与‎考试大纲第一部分考试说明1.考试性质全国硕士研‎究生入学考‎试是为高等‎学校招收硕‎士研究生而‎设置的。

电路（电气工程）是电气工程‎学科最重要‎的基础理论‎知识，为报考本学‎科硕士研究‎生的一门必‎考专业课，以满分15‎0分计入入‎学初试总分‎。

通过该课程‎的考试以保‎证被录取者‎有扎实的专‎业基础知识‎和较强的分‎析问题能力‎。

二、考试的学科‎范围《电路（电气工程）》考试内容分‎为两个部分‎：第一部分为‎电路基础（占120分‎）；第二部分为‎电力系统、电机或电力‎电子三门课‎程的基本理‎论知识（占30分），考试时，考生在电力‎系统、电机或电力‎电子三门课‎程中仅限于‎选一门进行‎答题，多选无效。

考试要点见‎本大纲第二‎部分。

三、评价目标主要考查考‎生对电路基‎本理论、基础知识的‎掌握情况，运用各种方‎法分析电路‎的能力。

要求考生应‎掌握以下有‎关知识：1、明确电路的‎基本概念，理解电路中‎的两类约束‎关系。

2、熟悉电路的‎常用定理，并能灵活应‎用。

3、掌握分析电‎路的主要方‎法。

4、正确使用电‎工仪表和具‎备相关的电‎工测量知识‎。

5、掌握电力系‎统、电机或电力‎电子的基本‎理论，熟练使用电‎路相关分析‎方法解决实‎际应用问题‎。

四、考试形式与‎试卷结构1、答卷方式：闭卷，笔试。

2、答题时间：180分钟‎。

3、题型：填空题、简答题和计‎算题。

第二部分考查要点一、电路基础考‎试内容范围‎1、电路模型和‎电路定律：电路基本概‎念、电压与电流‎的参考方向‎、常用的电路‎元件(电阻元件、电感元件、电容元件、电压源、电流源、受控源、运算放大器‎等)、基尔霍夫定‎律2、直流电路：电阻串联、并联、星形和三角‎形联结的等‎效变换、求解等效电‎阻的方法；用支路电流‎法、节点(结点)电压法、回路电流法‎列写方程，求解电路；灵活应用叠‎加定理、替代定理、戴维宁（诺顿）定理、互易定理、特勒根定理‎对电路进行‎分析和计算‎；含运算放大‎器电路的分‎析。

电气考研试题及答案一、选择题（每题2分，共20分）1. 下列关于电流的描述，正确的是：A. 电流的方向与电子流动方向相反B. 电流的方向与电子流动方向相同C. 电流的方向与正电荷流动方向相同D. 电流的方向与负电荷流动方向相同答案：A2. 欧姆定律的数学表达式是：A. V = IRB. V = I/RC. I = V/RD. I = VR答案：C3. 电磁感应定律是由哪位科学家提出的？A. 牛顿B. 法拉第C. 欧姆D. 安培答案：B4. 交流电的频率为50Hz，其周期为：A. 0.02秒B. 0.2秒C. 0.1秒D. 0.5秒5. 在三相交流电路中，星型接法和三角形接法的主要区别是：A. 电压大小B. 电流大小C. 电压和电流的相位关系D. 电压和电流的波形答案：C6. 以下哪种材料是半导体材料？A. 铜B. 石墨C. 硅D. 铝答案：C7. 电容器的单位是：A. 欧姆B. 法拉C. 亨利D. 伏特答案：B8. 变压器的工作原理是：A. 电磁感应B. 电磁转换C. 电磁辐射D. 电磁波答案：A9. 电感器的单位是：B. 法拉C. 亨利D. 伏特答案：C10. 以下哪种元件是无源元件？A. 电源B. 电阻C. 放大器D. 传感器答案：B二、填空题（每题2分，共20分）1. 在电路中，电阻的单位是_______。

答案：欧姆2. 电容器的充电时间常数由电容器的电容和_______决定。

答案：电阻3. 电感器的自感系数的单位是_______。

答案：亨利4. 交流电的有效值是其最大值的_______倍。

答案：1/√25. 根据基尔霍夫电流定律，在一个节点上，进入节点的电流之和等于_______。

答案：离开节点的电流之和6. 电磁波的传播速度在真空中是_______。

答案：光速7. 半导体材料的导电性介于_______和绝缘体之间。

答案：导体8. 在电路中，电流的单位是_______。

答案：安培9. 直流电的电压是_______的。

2021专业课真题一、选择题(1~20题，共40分)1.在利用栈将中缀表达式A-(B+C/D)×E转化成后缀表达式的过程中，当扫描到符号”)”时，栈中的内容是A(+/B-(+C-(/D-(+/2.现有一颗含有25个结点的4叉树T，若T中所有分支(即度不为0的)结点的度均为4，则T的叶子节点数是A15B17C19D213.下列序列中，不可能是任意二叉搜索树后序遍历序列的个数是①5,3,4,10,12,8②5,4,3,10,12,18③3,4,5,12,10,8④10,12,5,4,3,8A0B1C2D34.带权无向图G如下图所示，若分别用Prim算法(从顶点0开始)和Kruskal算法求G的最小生成树，则最后选中的边的权值分别是A5,3B3,5C5,4D5,55.已知序列25,13,10,12,9,5,6,8是大根堆，在插下新元素20的过程中，共进行比较操作的次数是A0B1C2D36.若数据元素序列9,10,11,8,5,12,2,4,7是采用下列排序方法之一得到的第二遍排序后的结果，则该排序算法只可能是A冒泡排序B选择排序C插入排序D二路归并排序7.若依次将关键码20,30,50,52,60,68,70插入到初始为空的3阶B树中，则最后得到B树的根结点中所包含的关键码是A50B52D60D50,528.下列关于机器字长的叙述中，错误的是A通用寄存器位数等于机器字长B系统总线宽度等于机器字长C主存单元长度不大于机器字长D ALU位数等于机器字长9.为了使计算机的数据传送和数据处理的功能可以并行实现，下列方法中有效的是A多种总线互联B以存储器为中心C多重存储器共存D以运算器为中心10.某计算机存储器按字节编址，主存容量配置为64KB，下列设计方案中，所用芯片的MOS 管门电路等基本元件性能相当，则性能最优的方案是A4片16KB×8位SRAM芯片B4片16KB×8位DRAM芯片C4片32KB×4位SRAM芯片D8片64KB×1位DRAM芯片11.下列寻址方式中，只能用于指令寻址的是A立即寻址B寄存器寻址C相对寻址D基址寻址12.下列有关微指令的叙述中，错误的是A垂直型微指令全部是功能性指令B垂直型微指令指令长度比较短C水平型微指令可完成多个微操作D水平型微指令显示表示顺序控制信息13.下列有关总线定时的叙述中，错误的是A异步全互锁定时方式的通信速度最慢B异步不互锁定时方式的通信可靠性最差C异步定时方式的握手信息可不通过联络信号产生D同步定时方式的时钟信号可由设备自行提供14.下列有关I/O接口的描述中，错误的是A每个I/O接口中至少包含一个I/O端口B一个I/O接口可以连接多个I/O设备C程序控制方式的I/O接口中可以没有状态口D不同I/O接口的I/O端口之间允许独立编址15.一个请求分页系统，测得如下利用率：CPU为5%，分页磁盘为97.5%，外设为4%，则下列措施中，可改善CPU利用率的是A更换速度更快的CPU B更换更大容量的分页磁盘C挂起内存中的某个用户进程D增加内存中的用户进程16.以下关于页式内存管理系统页面大小的叙述中，正确的是A页越大，页表也越大B页越大，则I/O开销越大C页越大，则内部碎片越大D页越大，则产生缺页中断的可能性越大17.某系统中有11台打印机，N个进程共享打印机资源，每个进程要求3台，为使系统不产生死锁，N的取值最多是A4B5C6D718.以下关于进程说法正确的是I.进程从运行状态转换到就绪状态，系统一定会发生CPU调度II.当I/O完成时，一个进程的状态有可能从等待状态转换为运行状态III.进程从等待状态转换为就绪状态，系统一定会发生CPU调度IV.进程进入终止状态，系统一定会发生CPU调度A I和IVB II和IIIC III和IVD IV19.页式内存管理系统中，物理内存地址为16位，逻辑地址为24位，页面大小为512B ，采用两级页表结构，外层页表有256页，则以下正确的是I.一个进程中最多有128个页II.一个进程中最多有32K 个页III.逻辑地址中表示外层页表、页号和页内偏移量的位数分别为8、7、9IV.逻辑地址中表示外层页表、页号和页内偏移量的位数分别为7、8、920.系统中四个进程(P1~P4)和三类资源(3个R1，2个R2，2个R3)，进程资源分配和请求状况如下表所示，则正确的是AllocationRequest R1R2R3R1R2R3P1100010P2020101P3100010P4002100二、综合应用题(21~32，共110分)21(8分)归并排序一般从用2路归并，即在两两归并过程中，从两个有序子序列中逐次挑选关键字最小的元素。

东南大学电气工程及其自动化考研XX东南大学电气工程及其自动化考研电气工程是现代科技领域中的核心学科之一，属于工学领域。

它是当今高新技术领域中不可或缺的关键学科。

传统的电气工程定义为用于创造产生电气与电子系统的有关学科的总和。

此定义本己经十分宽泛，但随着科学技术的飞速发展，21世纪的电气工程概念己经远远超出上述定义的范畴，斯坦福大学教授指出：今天的电气工程涵盖了几乎所有与电子、光子有关的工程行为。

本领域知识宽度的巨大增长，要求我们重新检查甚至重新构造电气工程的学科方向、课程设置及其内容，以便使电气工程学科能有效地回应学生的需求、社会的需求、科技的进步和动态的科研环境。

①101思想—理论②201英语一③301数学一④954电路（电气工程）554专业综合（电力系统基础、电力电子技术、电机学三选二）01电机与电器02电力系统及其自动化03高电压与绝缘04电力电子与电力传动05电工新理论06应用电子与运动控制技术07电气信息技术08新能源发电技术与分布式电源09智能电网理论与技术xx电气工程专业课考研参考书目：《电路》邱关源高等教育出版社《电路基础》黄学良机械工业出版社《东南大学954电路历年考研真题及答案解析》《XX东南大学954电路考研复习精编》（含真题与答案）《xx东南大学954电路考研冲刺宝典》《xx东南大学954电路考研模拟五套卷与答案解析》《XX东南大学电气工程学院考研复试一木通》xx年总分：335, __ /外语：50;业务1/业务2： 90;xx年总分：330, _/外语：50;业务1/业务2： 80;电路复习不用太早，八月份开始足以，因为电路资料少，真题有限，如果很早就把电路教材，参考书和真题搞定了，到最后快要考试的黄金时期自己容易迷茫，对自己是没有好处的，再说在—月份之前还有英语和数学两门课要打好基础，所以八月份开始复习电路理论绝不为晚！8月~9月：两个月把电路课本复习两到三遍，电路课本一定要复习的扎实，这样在以后的考研过程中会容易得多。

954《电路（电气工程）》~2016年启用时间：2016-06-17全日制硕士研究生入学954《电路（电气工程）》课程复习与考试大纲第一部分　考试说明1.考试性质全国硕士研究生入学考试是为高等学校招收硕士研究生而设置的。

电路（电气工程）是电气工程学科最重要的基础理论知识，为报考本学科硕士研究生的一门必考专业课，以满分150分计入入学初试总分。

通过该课程的考试以保证被录取者有扎实的专业基础知识和较强的分析问题能力。

二、考试的学科范围《电路（电气工程）》考试内容分为两个部分：第一部分为电路基础（占120分）；第二部分为电力系统、电机或电力电子三门课程的基本理论知识（占30分），考试时，考生在电力系统、电机或电力电子三门课程中仅限于选一门进行答题，多选无效。

考试要点见本大纲第二部分。

三、评价目标主要考查考生对电路基本理论、基础知识的掌握情况，运用各种方法分析电路的能力。

要求考生应掌握以下有关知识：1、明确电路的基本概念，理解电路中的两类约束关系。

2、熟悉电路的常用定理，并能灵活应用。

3、掌握分析电路的主要方法。

4、正确使用电工仪表和具备相关的电工测量知识。

5、掌握电力系统、电机或电力电子的基本理论，熟练使用电路相关分析方法解决实际应用问题。

四、考试形式与试卷结构1、答卷方式：闭卷，笔试。

2、答题时间：180分钟。

3、题型：填空题、简答题和计算题。

第二部分　考查要点一、电路基础考试内容范围1、电路模型和电路定律：电路基本概念、电压与电流的参考方向、常用的电路元件(电阻元件、电感元件、电容元件、电压源、电流源、受控源、运算放大器等)、基尔霍夫定律2、直流电路：电阻串联、并联、星形和三角形联结的等效变换、求解等效电阻的方法；用支路电流法、节点(结点)电压法、回路电流法列写方程，求解电路；灵活应用叠加定理、替代定理、戴维宁（诺顿）定理、互易定理、特勒根定理对电路进行分析和计算；含运算放大器电路的分析。

3、正弦交流稳态电路：正弦量的相量表示法、电路定律的相量形式、相量图、阻抗、导纳；能对一般正弦交流电路、含互感和变压器元件的交流电路、三相交流电路、非正弦交流电路等进行分析和计算；能计算正弦电路的瞬时功率、有功功率、无功功率、视在功率和复功率；电路的功率因素及其提高方法；串联、并联电路的谐振。

电气工程考研试卷真题一、选择题（每题2分，共20分）1. 在三相电路中，星型连接的三个相电压之和为：A. 0VB. 220VC. 380VD. 无穷大2. 以下哪个不是电力系统的基本组成元素？A. 发电机B. 变压器C. 电动机D. 继电器3. 变压器的原边和副边的电压比与它们的匝数比的关系是：A. 正比B. 反比C. 无关D. 非线性关系4. 以下哪个是电力电子器件？A. 二极管B. 三极管C. 晶闸管D. 以上都是5. 直流电机的励磁方式主要有：A. 他励B. 并励C. 串励D. 所有选项6. 以下哪个不是电力系统稳定性分析的内容？A. 静态稳定性B. 动态稳定性C. 瞬态稳定性D. 经济稳定性7. 电力系统中的短路电流计算主要考虑的是：A. 电流的大小B. 电流的方向C. 电流的频率D. 电流的相位8. 以下哪个不是电力系统的保护装置？A. 断路器B. 熔断器C. 继电器D. 变压器9. 电力系统中的负荷预测通常采用哪种方法？A. 统计分析法B. 经验估计法C. 专家咨询法D. 所有选项10. 以下哪个是电力系统的自动化设备？A. 变电站自动化系统B. 调度自动化系统C. 配电自动化系统D. 所有选项二、简答题（每题10分，共30分）1. 简述电力系统的基本功能和组成。

2. 解释什么是电力系统的短路，以及短路对电力系统可能造成的影响。

3. 描述直流电动机的工作原理及其主要应用领域。

三、计算题（每题25分，共50分）1. 假设有一个三相四线制的星型连接系统，其线电压为380V，相电流为10A，求系统的功率因数为0.8时的有功功率和无功功率。

2. 给定一个单相变压器，其原边电压为220V，副边电压为110V，原边电流为5A，求变压器的匝数比和功率。

四、论述题（共30分）1. 论述电力系统自动化的重要性及其在现代电力系统中的作用。

五、案例分析题（共30分）1. 某电力系统在运行过程中发生了一次大规模的停电事故，请分析可能的原因，并提出相应的预防措施。

3、东南大学《电路基础》本科教学大纲
东大954电路虽然考查知识点不多，但是试题很有难度，计算量较大，建议早点复习，复习时参考东南大学本科生《电路基础》教学大纲和东南大学954电路《考试大纲》。

4、2016年校内答疑知识点
含2016年校内答疑老师透露的知识点，对想考研省力的学生很有帮助！
三、东南大学《电路（电气工程）》考研复习题
1、《电路基础》课后习题详解答案
黄学良的电路课本的习题答案详解（考过原题，而且是本校用书，有一定参考价值）
2、电路考研大串讲习题答案
电路大串讲习题答案详解（综合985高校的考研题目，经典之极，助你达到新的高度！）
四、赠送资料（电子版，发邮箱）
第一部分：专业课
第二部分：公共课
以下为截图及预览：
2015年考研真题：
2014年考研真题：
2015年真题答案：
2014年真题答案：
考研复习笔记：
考研复习题：。

目录Ⅰ历年真题试卷 (2)东南大学2010年招收硕士学位研究生入学考试试卷 (2)东南大学2011年招收硕士学位研究生入学考试试卷 (8)东南大学2012年招收硕士学位研究生入学考试试卷 (13)Ⅱ历年真题试卷答案解析 (19)东南大学2010年招收硕士学位研究生入学考试试卷答案解析 (19)东南大学2011年招收硕士学位研究生入学考试试卷答案解析 (33)东南大学2012年招收硕士学位研究生入学考试试卷答案解析 (45)Ⅰ历年真题试卷东南大学2010年招收硕士学位研究生入学考试试卷请考生注意：试题解答务请考生做在专用“答题纸”上！做在其他答题纸上或试卷上的解答将被视为无效答题，不予评分。

科目代码：954科目名称：电路（电路工程）一、填空题（每题6分，共60分）1.如图所示，已知)60100cos(2220)(1︒+=t t u (V)，L 1=L 2=0.4H ，M=0.1H ，当)()(21t u t u =时，求C=F 。

图12.图示稳态电路中，U=10V ，I=50A ，P=400W ，P 1=300W ，Q 2=100Var ，电路呈容性，试求I 1=A ，I 2=A 。

图23.图示电路中，a 图中的网络N 的伏安特性曲线如图b 所示，试给出网络N 的诺顿等值电路表达式。

图34.图示电路中，R1=1Ω，R3=3Ω，U S1=1V，I S2=2A，R2可变。

若要使R2改变时，各支路电流不变，试求U S3=V。

图45.图示电路中，L1=1H，L2=2H，M=0.5H，i S为周期函数其波形如图b所示，则电压表的读数为V。

图a图b图56.图示电路中，运放为理想运放，求u0=V。

图67.N 0为无源线性定常系统，已知当)(2t u S ε=V 时，响应)2(2t e i --=A ，t≥0；当)(3t u S ε=V 时，响应)23(2t e i --=A ，t≥0；试求u S 为图b 所示波形时的响应i =A 。

共 45 页 第 1 页东 南 大 学 考 试 卷（A 卷）课程名称电工学 考试学期 11-12-2得分适用专业 机械工程及自动化 考试形式 闭卷 考试时间长度120分钟1)Birds routinely land and relax on power lines whichcarry tens of thousands of volts of electricity. Explain why these birds do not get electrocuted. (6 pts)The resistance of the air is too large for current to flow from the line to the bird to the ground.Alternately, the resistance is too large for current to divert from the wire, into the bird, and then back into the wire. It is not because of wire insulation. Birds could land on uninsulated wires just fine.6 pts for right answer. 1 pt for something vaguely correct.2) Suppose your car battery is dead, and you need to charge it using another car’s battery. You have a pair of cables 电缆which you can use to connect the terminals终端of the batteries. In order to charge your car battery, should you connect the same terminals (positive of one battery to the positive of the other, and the same with the negative) or the opposite terminals (positive of one battery to the negative of the other battery)? Why did you choose this configuration配置；结构? (6 pts)First note that real batteries have internal内部的resistance, so the universe领域will not explode爆炸if you directly connect two car batteries.Next, if the opposite terminals are connected, then P=VI and common sense tells us that both batteries will be supplying power, and the internal resistances will be consuming消耗power, so clearly no power is being delivered 递送by either battery. If the same terminals are connected,共45 页第 2 页then we can see that if one battery is of a higher voltage than the other, it will provide power to theother battery. Key to this realization实现is to know that battery voltages drop下降；终止as the battery is depleted耗尽的.6 pts for right answer. 2 pts if you try to say there is no current if two batteries are connected + to+ because voltage sources are perfectly balanced.3) A standard procedure for testing the internal resistance of a battery is the “dual双重的pulse脉冲” test. We first attach an ideal 5 mA current source between the terminals of the battery, so that current flows in the usual direction (positive to negative), and measure the voltage across the battery terminals. We then remove the 5 mA source, and attach an ideal 505 mA current source instead,and again measure the battery terminals. (6 pts)共45 页第 3 页i.Suppose that we find a 1.485V voltage with the 5 mA source, and a 1.385 with the 505 mA source, what is the internal resistance?Easy way to solve these is to subtract减去；扣掉 2nd from first, giving, or .3 pts for right answer. 2 pts if sign error or algebra 代数学mistake.ii. Assuming the battery is perfectly linear 线型的(i.e. accurately modeled 模式化；被效仿by a Thevenin 戴维宁equivalent), is it possible to find the voltage provided by the battery with no load attachedusing the data above? If so, what is it? If not, why not?共45 页第 4 页Plug塞住；用插头将与电源接通 in to one of our equations above, e.g., giving , or finally. If you did it with the current source the other way, you should still have gotten 1.486V.3 pts for right answer.Find the Thevenin or Norton equivalent circuit model.(12 pts ).共45 页第 5 页(6 pts )(6 pts )Find the Voltage v and the currents i1 and i2 for the circuit shown below. (10 pts )共45 页第 6 页SolutionLabel标注 the meshes；网状物:Since i3=2 it is not a variable.Writing KVL around the first mesh:24*(i2-i3) + 12*i1 = 0Writing KVL around the second mesh:12*i2 + 6*(i2 –i3) = 0Substituting代替，取代 for i3 and rearranging 36*i1 = 4818*i2 = 12共45 页第7 页Namelyi1 = 4/3 Ai2 = 2/3A7. Find the current i for the circuit shown below (10 pts )SolutionZeroing the 1A source gives共45 页第8 页By the current division principle, the contribution of the 2A source to i1 is2*(-1/30) / (1/30+1/5) = -2/7A.Zeroing the 2A source givesBy the current division principle, the contribution of the 1A source to i1 is1*(1/15)/(1/15+1/20) = 4/7A.Hence i1 = 4/7-2/7 = 2/7A.共45 页第9 页Find the Thevenin and Norton equivalent circuits across terminals a and b for the following circuitWith an open circuit across terminals a and b the current through the 20 resistor must be 0.5ix and the voltage across it is then 10ix. ByKVL we also get30V = 5ix + 10ixSo ix = 2A and we calculateVTH = 10ix = 20VTo find RTH we zero the independent独立的 source to get the circuit in Figure 4.We wish to determine what resistance this circuit isequivalent 等价的to across共45 页第10 页the terminals a and b. One way to do this is to imagine connecting anindependent voltage source of voltage VS across the terminals and findingthe current drawn from this voltage source. We therefore consider thecircuit in Figure 5.KVL gives−5Ωix = VS → ix = −VS/5Ω A (1)KVL also gives20Ωi1 = VS → i1 =VS/20 Ω (2)KCL givesi = i1 + 0.5ix − ix = i1 − 0.5ix (3)共45 页第11 页Plugging (1) and (2) into (3) yieldsi =VS/20Ω+VS/10Ω=3VS/20ΩEventually,RTH =VS/i=20/3 ΩThe Thevenin equivalent circuit is depicted描述； in Figure 6.From this we get the Norton equivalent circuit in Figure 7 where we usedWe could have also determined IN by applying a short circuit across theterminals a and b and computing 计算；处理the current through the short circuit短路.This involves analyzing the circuit in Figure 8. Here wehave by KVL共45 页第12 页5ix = 30V → ix = 6AThis gives, by KCLi = ix − 0.5ix = 0.5ix = 3Awhich matches the earlier calculation计算；估计.Suppose that v1(t) = 80 cos (ωt) and v2(t) = 60 sin (ωt). Use phasors相量 to reduce the sum vs(t) =v1(t) + v2(t) to a single 单一的term of the form Vm cos (ωt +θ). Draw a phasor diagram, showing V1, V2, and Vs. State the phase relationships between each pair of these phasors. (16共45 页第13 页pts )The phasor corresponding tov1(t) = 80 cos (ωt)isV1 = 80∠0 = 80Equivalently, we get forv2(t) = 60 sin (ωt) + 60 cos (ωt −π/2)the phasorV2 = 60∠−π/2 = −j60To find the sum using phasors we add the complex numbers which yieldsV = V1 + V2 = 80 − j60 = 100e−j arctan 3/4This corresponds符合，一致 to the time signalvs(t) = 100 cos (ωt − jarctan3/4)The phasor diagram is depicted描述 in Figure 2.Note that V1 leads V2 by π/2 and leads Vs by arctan反正切 ( 4/3 ).共45 页第14 页Find an expression 表达式for v(t) of the form Vm cos (ωt +θ) when v(t) = v1(t) + v2(t) + v3(t) + v4(t) withv1(t) = 20 sin (ωt)v2(t) = 20 cos (ωt +π/6)v3(t) = 20 sin (ωt +π/3)v4(t) = −10 cos (ωt)Use phasors. (6 pts )Solution:The phasors corresponding 相应的to each component 成分；组件；[电子] 元件signal are given in Table表格 1. The complex number equivalent复数等效to each phasor is given as well.共45 页第15 页Adding all complex numbers giveswhich corresponds to the phasorwhich can be transformed变形 into the time signalFind the complex impedance阻抗 in polar form 点斜式极坐标形式极形式of the network shown below for ω = 10001/s , ω= 20001/s ,and ω = 40001/s . (6 pts )共45 页第16 页(5 pts)Both capacitors电容器 and inductors电感器 can be used to store energy for use later. Capacitors, though, are far more popular for energy storage than inductors, because they are easier to keep charged带电荷的带电的. In lab, for example, you can easily connect up a capacitor to a battery, disconnect it from the source, carry it around in your pocket to grab lunch午餐, go back to lab, and then find that it's still holding a charge even after a long time. Explain why this is relatively difficult with inductors.共45 页第17 页(5 pts) If you've ever had the batteries on a flash li ght闪光灯；手电筒 run out,you know that as soon as the ligh t starts dimming调光；变暗,your battery will very soon be dead.This is because a battery supplies its maximum vo ltage峰点电压 until right before it is depleted耗尽的.On t he axis 坐标轴on the left,I have plotted标绘的 the brightn ess亮度辉度 of a battery powered flashlight over the lif e of the battery.We can also power a flashlight using共45 页第18 页a capacitor.Assuming the brightness of a bulb 电灯泡is p roportional比例的 to the voltage across it,on the right axis,draw (qualitatively定性地) the brightness vs. Time for a capacitor powered flashlight.Draw so that bright ness is 1 at time=0,and has dropped to at least 0.1 by time=1.We just want the shape形状,not necessarily the exact values.c) (5 pts) A student is not satisfied with the amount of共45 页第19 页energy stored in his one-capacitor circuit. He wants to store more energy, so puts 10 capacitors in series串联 and charges them with a single voltage source. Is this a good idea? Why or why not?Find the Thevenin equivalent 戴维南定理of the circuit电路below at the two terminals on the far right:共45 页第20 页e) Find the Thevenin equivalent of the circuit below between terminals and [Think about the various algorithms算法 we’ve used to find Thevenin equivalents.If you get stuck被困住了,complete the rest of these tricky 棘手的复杂的problem and come back to this one and maybe some inspiration will reach you]:共45 页第21 页共45 页第22 页For the circuits below, please find expressions for the specified voltage表达式指定的电压over the indicated time 表示时间ranges in terms of the circuit parameters电路参数. Plot 绘图 the waveform 波形图on the provided axes轴线, and clearly identify. 确定 the key parameters参数 in your graph图表. (3A) Consider the circuit of Fig. 4. The switch is open for t <0, closed for 0≤t < t1, and open for t ≥t1, where t1 = 3RC. Find and plot the voltage v C (t).共45 页第23 页(3B) Consider the circuit of Figure 5, in which > -1.共45 页第24 页The switch is open for t <0, and closed for t 0. vC(0-) = V0. Find and plot the voltage v1(t).共45 页第25 页The circuit shown in Figure 4 has been at rest with theswitch open for a long time. At t = O the switch is closed.共45 页第26 页Sketch 素描；略图；梗概the current ic集成电路 through the capacitor for t > O on the axes below. Using the circuit parameters R1, R2, C, and Vo,indicate on your sketch (i) the initial value初始值 ic(Ot), (ii) the final value ic(oo), and (iii) the time constant时间常数.共45 页第27 页Problem 1F: 5 pointsThe capacitor in the circuit in Figure 6 has an initial初始最初的voltage V O on its terminals at t =0−when a step of voltage Vu(t) is applied at t = 0. Find an expression for the voltage across the capacitor v C for t> 0.共45 页第28 页Consider the current divider circuit分流电路 shown below:共45 页第29 页1a. How many branches分支 are there in the circuit?1b. How many nodes节点 are there in the circuit?2. Derive an expression派生一个表达式 for the output current 输出电流(Iout, shown above) as a function of theinput current (Iin) and the two resistors (R1 and R2). Use any technique you’d like.3. How should the resistors be chosen such that twice as much current flows throughR1 compared to R2?4. Using the equation 方程等式you obtained in #2, show what happens to Iout输出电流 if R2 is replacedwith a short circuit (i.e. R2 = 0). Repeat if R2 is replaced with an open circuit.(think about what R2 should be replaced with here) Now suppose the following values are used: Iin = 3 A, R1= 5 , R2 = 20 , and we wish to find the Thevenin共45 页第30 页equivalent circuit across the two indicated terminals below:5. Find Voc and Isc across the two terminals indicated on the circuit.6. Draw the Thevenin equivalent circuit for the two terminals indicated above.7. Suppose a load is now attached across the two terminals of the Theveninequivalent circuit:a. Write an equation for I in terms of V.b. Sketch the IV characterstics伏安特性. Use I as the“y-axis Y轴” and V as the“x-axis”. Label标注all relevant points相关点.共45 页第31 页8. Suppose the load has an IV characteristic given as follows:a. What are the values of I and V if the load is attached to the Thevenin equivalent circuit ] 等效电路?b. Looking at the IV characteristic, what is the load? (describe the load as much as you can)For problems 9 through 12, consider the following circuit:9. Using KVL and mesh analysis, write down the equations needed to solve the circuit. Convert转变the resistor voltages into currents.10. The dependent source requires one additional equat共45 页第32 页ion附加方程to be generated产生. Write down that equation by looking at the 3 resistor.11. Solve the equations simultaneously同时地to determine the two mesh currents网孔电流.12. To check your answer, confirm确认that power is conserved 守恒in the circuit. Find the power dissipated浪费的in each resistor. Find the power generated生成的(or dissipated in each source). Be clear in your answers whether power is being generated or dissipated in each circuit element. For problems 1–7, consider the following circuit:1. Find the transfer转移function, i.e. Vout输出电压()/Vin(), in terms of R, L, and .2. What is the magnitude大小of the transfer function传递函数, i.e. | H() |, in dB?3a. What is | H() | equal to (in dB) for very low共45 页第33 页frequencies频率?3b. What happens to | H() | at high frequencies? What kind of a filter滤波器do we have here?4. Derive the equation for the break frequency推导出方程为截止频率. The break frequency is definedas the frequency where | H() | = –3.0103 dB.5. Sketch the magnitude Bode波特图plot for this filter滤波器. Label标注all critical points andslopes. Show how you obtained the value for any non-zero slopes零斜坡.6. Suppose R = 1 , L = 2 H, and Vin = 3 cos(5t + 30o). Find Vout(t).7. Draw a phasor diagram, indicating the voltage and current phasors of all thecircuit elements电路参量.For problems 8–12, consider the following circuit:共45 页第34 页8a. Find the current that appears on the output side ofthe transformer变压器.8b. What is the voltage that appears across the capacitor. (phasor form is acceptable,assume an angular frequency角频率of 1 rad/s)9. Find the voltage that appears on each side of the transformer.10. Find the voltage that appears across the current source.11. Replace the transformer and input circuitry with an equivalent current sourceand inductor. In other words, draw a circuit which will have a current source,an inductor, and a 3 F capacitor all in series. Label the values for the current source and the inductor.Check your answer to #11 by comparing the amount of power共45 页第35 页generated by the currentsource in each circuit.12. Find the amount of power generated by the current source in the new circuit.Compare this with the amount of power generated by the current source in theoriginal circuit原电路 (they should be the same)For problems 4–7, consider the following circuit:4. Find the transfer function, i.e. Vout ()/Vin (), in terms of R, L, and (or f).5. What is the magnitude of the transfer function, i.e. | H() |?共45 页第36 页6. What is | H() | equal to for very low frequencies? For very high frequencies?What happens at resonance谐振? (i.e. = o =LC1) What kind of a filter滤波器do we have here?7. Sketch the magnitude Bode plot for this filter. Label all critical points andslopes斜率. Use R = 2 , L =41H, and C =81F. Show how you obtained the valuefor any non-zero slopes.In order to measure the voltage across a resistor in a circuit, a voltmeter电压表is used.Although we assume an ideal voltmeter in most cases, a real voltmeter has a finite有限的resistance (R3) which can have an effect on your circuit. Consider the followingmeasurement on a voltage divider分配共45 页第37 页Vin, R1, and R2 are just the standard elements of a voltage divider.1a. How many nodes are there in the circuit?1b. How many meshes are there in the circuit?2. Write a KCL equation at node A. Convert the currents into voltages.3. Solve the equation for Vout, so that you have an equation for Vout based onVin, R1, R2, and R3.4. Show that as R3 approaches infinity无限大(i.e. R3 ), you get the standardequation for a voltage divider.For problems 5 through 11, consider the following circuit:共45 页第38 页Find the Norton equivalent circuit, as follows:5. Short circuit the two terminals and redraw the circuit without the 2 resistor.Explain why the 2 resistor can be dropped from the circuit.放弃了电路6. Use node analysis to find Isc. (You will need to come up with one additionalequation to eliminate消除ix and get a numerical数字的answer) 7. Now consider the circuit when the two terminals are open circuited. Using meshanalysis, find ix under these conditions.8. Using your results from #7 (or using node analysis, which will take more time),find Voc, the voltage across the two terminals in an open circuit condition.共45 页第39 页9. Confirm that power is conserved in the circuit under open-circuit conditions.Find the power dissipated in each resistor. Find the power generated (ordissipated in each source). Be clear in your answers whether power is beinggenerated or dissipated in each circuit element.10a. Draw the Norton equivalent circuit. Label values for all circuit elements.10b. Draw the Thevenin equivalent circuit. (Note: you already have everything youneed)11a. Assume that a circuit element (that draws some current I and has somevoltage drop V) is attached to the terminals of the Norton equivalent circuit.Using KCL, write an equation for I in terms of V.11b. Graph the IV relationship (i.e. the load line). Use I as the “y-axis” and V as the共45 页第40 页“x-axis”. Label all relevant points.For problems 1–5, consider the following circuit:Use Vin = 100 v, R1 = 1000 , R2 = 250 , R3 = 1000 , and C = 1 F. At t = 0, theswitch is moved down, disconnecting R1 and connecting R2 to the circuit. We want to find the voltage v(t), and current i(t), across the capacitor as a function of time. 1a. Redraw the circuit, showing how the circuit looks just before the switch ismoved. Assume a long time has already elapsed before the switch is moved.1b. What is the continuity连续性condition for this circuit共45 页第41 页at t = 0?2. Using the circuit generated in #1a, find v(0–) and i(0–)3a. Find v(). Explain how you get this result.3b. Write a KCL equation for the circuit after the switch as been moved at t = 0.Convert the currents into voltages. (you should end up with a first-orderdifferential equation for v(t))4a. What form should the solution for v(t) take?4b. Substitute替代this solution into the differential equation generated in #3b. Use theresults of the substitution, along with the results for #1b and #2 to find all theconstants defined for v(t). (Clearly show your work) 5. Sketch curves of i(t) and v(t) as a function of time (t ). Indicate allcritical and asymptotic values.For problems 6–10, consider the following second-order共45 页第42 页circuit:The switch is opened at t = 0. The goal is to find the current through the inductor, i(t).6a. Assume that the switch has been closed for a long period of time. Find i(0–).6b. What should i(0+) be? Explain.7a. Find i(). Explain how you get this result. Draw the corresponding相应的circuitat this steady state condition.7b. Since this is a second-order circuit, another initial 初始/boundary condition is needed.Find that other value. Show your work.8. Derive导出the second-order differential equation for this circuit. Start by writing aKVL equation for the circuit after the switch has been opened. Then convert共45 页第43 页voltages in each passive element into currents.9a. What form does the solution for i(t) take?9b. Substitute your solution into the differential equation. Solve the correspondingcharacteristic equation.相应的特征方程10. Finish determining i(t) by using the results in #6b and #7b to find any constantsyou have defined in your solution for i(t).For problems 1–5, consider the following circuit:Use Vs = 5 v, R1 = 5 , R2 = 10 , and L = 1 H. After a long time has elapsed, theswitch is opened at t = 0. We want to find the voltage v(t), and current i(t), across共45 页第44 页R2 as a function of time.1a. Redraw the circuit, showing how the circuit looks just before the switch isopened.1b. Using this result, find v(0-).2a. What is the continuity/boundary condition for this circuit at t = 0?2b. Find the numerical value of the boundary condition.3. Write a KVL equation for the circuit after the switch as been opened at t = 0.(note: do not use the circuit you drew in #1a). Convert the voltages into currents.4. Solve the differential equation generated in #3 for i(t). Clearly show how youobtained all of the numerical values in i(t).5. Sketch curves of i(t) and v(t) as a function of time (t ). Indicate allcritical and asymptotic渐近的values.共45 页第45 页。

专业课复习的一点经验之谈最近几天，和几个17年的考生谈了一下东南电气考研专业课的情况，顺便总结了一下自己复习时候的经验和教训，感觉大家普遍挺关心这个问题的，就打算写这篇帖子。

主要是想给大家一点建议，当然适不适合，各位可根据自己的情况，做出合理的安排！（1）专业课都是各院校自己阅卷的，像东南这种学校，竞争比较激烈，学校为了使分数线看起来没那么高，专业课阅卷会比较严一些，就是俗称的压分！一般120、130左右就算是高分了，觉得自己学得不错、发挥得不错，结果成绩出来后是90、100左右的也不在少数！好在东南阅卷是很公正公平的，外校的考生大可以放心，复试也是很公平的，不会有什么排外现象的！（至少我觉得是这样）。

注意一点，专业课考试每个题目的分值很大，如果粗心做错了题，扣分比较严重（学校本来就想压分），一不小心十几分就没了，最后分值就会跟自己预想的差很多，所以，一定要细心啊！（2）关于954电路的复习资料，我用过的主要包括四部分：邱关源课本和课后题、黄学良课本和课后题、20多年初试真题、考研大串讲！建议时间安排如下：（只是建议，重要的是大家要有自己的计划）【1】6、7月份把邱关源的课本看一遍，课后题都做一遍；如果时间不够，课后题可以选做一部分（我当时是全都做了），把做错的题目标记下来，留待以后重温！【2】8、9月份看黄学良版的课本，这本课本是东南大学的校内教材，和邱关源的内容基本上差不多，但有些章节侧重点有些不同，会让你有耳目一新的感觉！前几年黄学良担任东南电气学院院长的时候，据说考研初试还考过课后题的原题或类似的题目！（现在院长换人了，不知道东南本科教材有没有换，但个人感觉有必要看一遍，权当是电路知识的第二遍复习了）！边看课本边做课后题，这个时候还可以把邱关源课后题的错题同时再做一遍！利用这两个月，搞定这两本教材和相应的课后题，打下电路的坚实基础！【3】10月份的时候就主攻真题！坚持每天一套，模拟考试情形，一定要在3个小时甚至更短的时间内完成！做完一遍之后，这个月应该还没过完，可以重温一下真题里的错题！真题可以留最近三年的三套题到最后一个月用来模拟！【4】11月份的时候做考研大串讲！这本书整理了各个高校的电路考研历年真题，题目质量都很高，难度也不小，各个学校考研试题之间会相互借鉴，所以个人感觉这本书价值也很高，要好好利用！另外，好像还有一本陈燕编写的辅导书，据说性质和大串讲差不多，也不错，这本书我没有用过，大家要是有时间可以做做看！【5】12月份直到考研，在这不到一个月的时间里，大家可以模拟之前预留的三套真题，把之前的错题做一遍，回顾一下知识点，再做一些没看完的辅导书（大串讲或陈燕的书），这个时候尤其注意心态的调整，不要想着有多少题目还没有做，题目各式各样，永远都做不完的，要调整好心态，按部就班地复习，因为不见得题目做得多就考得好！然后再说一下新增的三选一的情况：三选一一共占30分，我选的电机学，题型主要包括填空（10×1）、简答（2×5）、计算（1×10），另外两科情况也是差不多的。