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专业课程展示

可能出现基础问题

自我介绍(self-introduction)

Good morning, nice to meet you here. my name is xxx. I’m a senior student in xxx university. My major is Electronic Information Engineering.I like making or controlling machines.That’s why I choose my major. my objective is obtain a master of degree hardware design and development in German.

你想申请哪所大学?

I want to apply for the universities such as Karlsruher Institut für Technologie,which has a good academic reputation and excellent professors.Also university of stuttgart and Technical University of Munich are included. They are all very good universities.

为什么选择到德国留学?

German universities have advanced equipments and good study enviroment, which can help me learn my professional knowledge better. At the same time, I want to experience international cross-culture. As you konw, word is becoming samller and closer due to the quickly developing technology.

学费谁来负担?

My parents will pay the tuition for me. And they have already prepared enough money for my aboard study.

专业课程资料准备

电路

在这门课中,我主要学习了电路的基本元器件,分析电路的一些定律和定理。

In this course, I mainly learned the basic components of the circuit and some laws and theorems of the circuit analysic.

电路的基本元器件(basic components of the circuit)

电阻(resistor)

在电压和电流取关联参考方向时,在任何时刻其两端的电压和电流服从欧姆定律。欧姆定律指出通过电阻的电流跟电阻两端的电压成正比,和电阻成反比。U = R*i

When the voltage and current take the correlation reference direction,the voltage and current at both of resistor obey Ohm’s laws at any given moment. Ohm’s law states that the current across the resistor is directly proportional to the voltage at the both ends of resistor and inversely proportional to the resistor.

R是电阻元件的参数,是一个正常的实数,单位是欧姆。电阻的倒数称为电导,i = G*u,电导的单位是西门子,R和G都是电阻元件的参数。

R is the parameter of resistor and it’s a positive constant real number. The unit of resistance is ohm. The reciprocal of resistance is conductance and the conductance is simens. R and G are both the parameter of resistor.

电阻元件的特性称为伏安特性,它的特性曲线是一条通过原点的曲线,直线的斜率与元件的电阻R有关。

The characteristics of resistor is called volt-ampere characteristics . The characteristics curve is a straight line passing through the origin the slope of the line is related to the resistance of component.

当一个线性电阻元件的端电压无论为何值时,流过它的电流恒为零值,则该电路开路。

When the terminal voltage of a linear resistance element is no matter any value,the current flows through it is always zreo. So the circuit opens.

当一个线性电阻元件的电流无论为何值时,它的端电压恒为零值,则该电路短路。

when the current of a liner resistance element is no matter any value,the terminal voltage of it is always zero. So the circuit is short out.

关联参考方向:电流的参考方向自电压的正极性端流入电路,负极性端流出,两者的参考方向一致,则是关联参考方向。参考方向是人为指定的方向。因为电流或电压的实际方向是未知的,设定参考方向后,可通过值的正负来反映电流的实际方向。

Correlation reference direction: The reference direction of the current flows the positive end of the voltage into the circuit and flows out from the negative end. Then the reference direction of the two are the same, so the reference direction is related. The reference direction is specified artificially.Because the actual direction of the current or voltage is unknown, after setting the reference direction, the actual direction direction of the current can be reflected by the plus and minus of the value.

电容(capacitor)

电容器由间隔以不3同介质(例如云母和空气)的两块金属板组成。当在两极板上加上电压时,两极板上就会分别聚集起等量的正、负电荷,并在介质中建立电场而具有电场能。将电源移去后,电荷可继续聚集在极板上,电场继续存在。因而电容器是一种能容纳电荷的储能元件。

A capacitor consists of two metal plates spaced apart in different mediums(such as mica or air). When the voltage is added to the two polar plate, the same number of positive and negative charges are accumulated on the two polar and an electric field is established in the medium, which has the electric field energy. After the power is removed, the charge can remain concentrated on the plate and the electric field continues to exist. Thus, a capacitor is an energy storage component that can hold charges.

电容器储存电荷的能力称之为电容,电容等于电容器所带所带的电荷量q与电容器两极板上电压u的比值。C = q/u, 电容的单位是法拉F。

The capacity of a capacitor store charges is called capacitance. The capacitance is equal to the ration of the amount of charges carried by the capacitor to the voltage on the two plates of the capatior. The unit of capacitance is Farad.

如果电容元件的电流和电压取关联参考方向,则可以得到电流和电压的关系

i=du/dt=C*du/dt,表明电流和电压的变化率成正比。当电压不随时间变化时,电流为零。所以电容在直流情况下,其两端的电压值恒定,相当于开路。也就是说电容有隔断直流的作用。

电容的串联类似于电阻的并联,电容的并联类似于电阻的串联。

If the current and voltage of the capacitor component take the correlation reference direction, the relation between the current and the voltage can be obtained, which indicates that the current is directly proportional to the rate of the voltage. When the voltage does not change with time, the current is zero. Therefore, when the capacitor is under the circumstance of DC , the voltage at both ends is constant, which is equivalent to open circuit. That is to say, the capacitor has the function of blocking the direct current.

The capacitors in series are similar to resistors in parallel. The paraller connection of capation is similar to the series of risistors.

当电容器与直流电流连接时,电路中有电流接通。两块金属板上分别会产生数量相同但极性相反的电荷,此时电容器正在充电。电容器两端的电压Vc会逐渐增大,一旦Vc增大至与电源电压V相等时,电容器充电完毕,电路中在没有电流流动。

When the capacitor is connected to the DC power supply, there is current flowing through the circuit. Two pieces of metal plates produce repectively equal but opposite charges. When the capacitor is charging, an equal number but opposite charges will be produced on the two plates. The voltage at the two ends of the capacitor increases gradually. Once the voltage increases to equal the supply voltage, the capacitor is charged and there is no current flowing through the circuit.

电容器充电的图像与 RC一阶电路的零状态响应一致,零状态响应就是初始状态为零,由输入信号引起的响应。

The image of capacitor charging is consistent with the zero-state response of the RC first-order circuit. Zero-state response is the response that caused by the input signal when the inital state is zero.

当切断电容器和电源的连接后,电容器通过电阻进行放电。两块金属板之间的电压会逐渐下降至零。(在电场力作用下,两金属板上的正负电荷不断中和,所以电压会不断下降)

When the connection between the capacitor an the power source is cut off, the capacitor is discharged through a resistor. The voltage between the metal plates will gradually drop to zreo. (Under the action of electric field, the positive and negative charges on the two metal plates are constantly nertralized, so the voltage drops continuously.)

电感(inductor)

电感是一种能够把电能转化为磁能并存储起来的元件,例如含有铁芯的绕制线圈。线圈通以电流后,在线圈内部会产生磁通,电感是线圈的磁通量与电流的比值。电感的单位是亨利H。

电感的串联类似于电阻的串联,电感的并联类似于电阻的并联。

An inductor is a device that converts electrical energy into magnetic energy and stores it. For example, a winding coil with an iron core. After the coil is charged with electricity, the magnetic flux will be generated inside the coil. The ration of the coil’s magnetic flux to the current is the inductance. The unit of inductance is Henry.

The indutors in series are similar to the serices of resistors and the shunt of inductance is similar to that of resistors in parallel.

当电感与直流电源连接时,突然增加的电流会使电感产生于电源相反的感应电动势,阻碍电流的改变,减慢的电流会使VL减小。当电流稳定后,不再产生感应电动势,VL降至零伏,此时电感器的储能完成。VL为0V,所以在直流电路中,电感器可等效为短路。电感器就像普通的导线,它的电阻值为零,而流过电感器的电流不能够突变。

When the inductor is connected to the DC source, the sudden increacse in the current will cause the inductor to generate a induced electromotive force that is opposite to the power supply. The induced electromotive fotce hinders the changes of the current and the slowed current will cause the decrease of voltage . When the current is stable, there is no induced electromotive force generated. The voltage drops to zero volt and the energy storage of inductor is finished. VL is zero volt, so in the DC circuit. the inductor flows through the inductor can’t mutate.

当电感与电源断开后,电压VL瞬间降至负值,但同时电流保持同一流动方向和大小。电感器通过电阻放能,VL逐渐上升至零,而iL逐渐下降至零。

When the inductor is disconnected from the power source, the voltage drops to a negative value instantaneously. But at the same time the current remains the same flow direction and size. Inductors release energy through resistors and VL increases gradually to zero while iL gradually decreased to zero.

分析电路的定律定理(laws and theorems of the circuit analysic)

KCL,基尔霍夫电流定理(Kirchoff’s Current of Law)

任何时刻,对电路中的任一个结点,流出该结点的电流之和等于流入该节点的电流之和。

For any node in the circuit, the sum of currents flowing into the node at any time equals to the sum of currents flows out the node.

KVL,基尔霍夫电压定理(Kirchoff’s Voltage of Law)

任何时刻,沿任一回路,所有的支路电压的代数和恒等于零。求和时,先需任意制定一个回路的绕行方向。凡支路电压的参考方向与回路的绕行方向一致,该电压前面取“+”号,相反则取“-”号。

Along any closed loop, the algebraic sum of all branch voltage at any time is identically vanishing. Before in summing of voltages, we need to specify a circuitous direction of the circuit,the voltage is positive. Othewise, the voltage is negative.

叠加定理(Superposition Theorem)

叠加定理指出在线性电阻电路中,某处电压或电流都是电路中各个独立电源单独作用时,在该处分别产生的电压或电流 的叠加。叠加定理只适用于线型电路,而不适用于非线性电路。在叠加的各分电路中,不作用的电压源置零,用短路代替,不作用的电流源置零,用开路代替。

Superposition theorem states that in the linear resistance circuit, a voltage or current is the supersition of valtage or current produced by individual independent power separately applied to the circuit. The superposition theorem applies only to linear circuit, but not to nonliear circuits. In the subcircuit of superimposed circuit, the non-working voltage source is set to zero and replaced by the short circuit and replaced by the short circuit. The non-working current source is set to zero and replaced by the open circuit.

戴维南定理(Thevenin’s Theorem/Norton’s Theorem)

一个含独立电源和线型电阻的一端口,对外电路来说,可以用一个电压源和电阻的串联组合或者电流源和电阻的并联组合来等效置换。此电压源的电压等于一端口的开路电压Uoc,电阻等于一端口全部独立电源置零后的输入电阻Req,电流源的电流等于一端口的短路电流Isc。

A port with independent sources and linear resistors can be equivalent replaced by a series combinations of valtage source ande resistors or parallel combination of current source and resistor for extermal circuits. The voltage of voltage source equal to the open-circuit voltage of prot. The resistor equals to the input resistors, when all the indepent sources ant the port are set to zero. The current of current source equal to the short-circuit current of the port.

电压源和电流源(Voltage Source & Current Source)

电压源是一个理想的元器件,电压源的电压U(t)与通过元件的电流无关,总保持给定的时间函数U(t) = Us(t)。当Us(t)为恒定值时,这种电压源称为直流电压源,用Us表示。

Voltage source is an ideal circuit compnent, the voltage of the voltage source is independent of the current through the componet and always keep a given time function. When it is a constant value, this voltage source is called a DC voltage source and is represented by Us.

电流源也是一个理想的电路元件,电流源的电流i(t)与元件的端电压无关,总能保持为给定的时间函数i(t) = is(t)。电流源在伏安特性曲线上是一条不通过原点且与电压轴平行的直线。当is(t)随时间变化时,这条直线将随之平移。

当i(t)=0就相当于开路,把is(t)≠0的电流源开路是没有意义的。

The current source is also an ideal circuit element. The current of the current source is indepent of the component’s terminal voltage and can always be maintained as a given time function. current source in the volt-ampere characteristic curve is a line that does not pass through the origin and is paralled to the voltage axis. When is(t) changes with the time, the line will move along.

When i(t)=0,the current source is equivalent to open-circuit. It is pointless to open the current source, which is not equal to zero.

电路分析实验内容

在实验课中,我们对叠加定理和戴维南定理进行了验证,并且观察力RC一阶电路的响应波形。

In experimental course, we verified the superposition theorem and Norton theorem and observed the response waveform of RC first-order circuit.

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