Verification of Kirchhoff's law and Multisim Simulation (engineering documents attached)

Catalog

3.1  The experiment purpose

3. 2  Experimental principle

3. 3  Experiment content and steps

3.4  Experimental requirements and precautions

3.5 Experimental report and thinking questions

---

3.1  The experiment purpose

1. Deepen the understanding of Kirchhoff's law ;

2. Learn how to use a multimeter to measure DC voltage and DC current , Verify Kirchhoff's law ;

3. Learn to measure the current of each branch with an ammeter .

3. 2  Experimental principle

Kirchhoff's current law （KCL）： Kirchhoff's law of current is the basic law of current . That is, at any time , In a lumped circuit , For any node （ Closed surface ） for , The algebraic sum of the currents of all branches is equal to zero , namely ∑I=0. If it flows into this node （ Closed surface ） The current is positive , Then it flows out of the node （ Closed surface ） The current is negative （ It can also be stipulated in reverse ）.

Kirchhoff's law of voltage （KVL）： For any closed circuit , The algebraic sum of voltage drop of all branches is equal to zero , namely ∑U=0. Usually , If the reference direction of branch or component voltage is consistent with the bypass direction of the circuit, it is positive , Whereas negative .

The form of Kirchhoff's law is applicable to circuits composed of various components , For both linear and nonlinear . When applying the above law, we must pay attention to the positive direction of current in each branch or closed circuit , This direction can be set arbitrarily in advance .

3. 3  Experiment content and steps

1. Verify Kirchhoff's voltage law

Select components , The structure is shown in the figure 3-1 The experimental circuit shown .

chart 3-1  Circuit diagram for verifying Kirchhoff's voltage law                     3-2  Circuit diagram for verifying Kirchhoff's current law

（1） First adjust the output of DC regulated power supply to 4.5V;

（2） After the circuit is connected , Measure the resistance in turn R1 and R2 Terminal voltage of U1、U2 And the current in the circuit I, Fill in the measurement data in the table 3-1 in , And ask for ∑U, Verify Kirchhoff's voltage law .

Take clockwise as the reference direction of current .

surface 3-1  Verify Kirchhoff's voltage law

	U（V）	U1（V）	U2（V）	I（mA）	ΣU
Theoretical value	-4.5	3	1.5	5	0
Measured value （ Internal resistance of voltmeter 1G o ）	-4.5	3	1.5	5	0
Measured value （ Internal resistance of voltmeter 1k o ）	-4.5	2.786	1.714	7.429	0

2. Verify Kirchhoff's current law

Select components , The structure is shown in the figure 3-2 The experimental circuit shown .

（1） First adjust the output of DC regulated power supply to 5V, Then put the circuit diagram 3-2 Connect it into a circuit diagram ;

（2） After the circuit is connected , Set the multimeter to DC current , Measure the current of each branch in turn , Fill in the measurement data in the table 3-2 in .

（3） When measuring current , Set the internal resistance of ammeter to 1n Oh and 1 Europe for measurement , Compared with the theoretical value , Compare the measurement results , Analyze the cause of the error .

The current direction takes the inflow node as positive , The outflow node is negative .

surface 3-2  Verify Kirchhoff's current law

3.4  Experimental requirements and precautions

1. verification KVL、KCL when , The voltage of the voltage source should also be measured , The values given in the experiment are only for reference .

2. Measure the voltage 、 When there is an electric current . Not only do you have to read the values . Also judge the actual direction , And compare with the set reference direction , If it's not the same , Then... Shall be added before this number “-” Number .

3.5 Experimental report and thinking questions

1． According to the experimental data , Select the closed loop in the experimental circuit , verification KVL The correctness of the ;

2． According to the experimental data , Select the nodes in the experimental circuit , verification KCL The correctness of the ;

3． Analyze the cause of error .

4． Thinking questions ：

（1） Measure the voltage 、 When there is an electric current . How to judge their sign ？ What is the meaning of the sign ？

answer ： Measure AC voltage 、 When there is an electric current , There is no difference between positive and negative . When measuring DC , It is related to the selected reference direction . When selecting the associated reference direction , If the calculated value is a positive number , It means current , Reference direction of voltage and current 、 The actual direction of the voltage is the same , If the value obtained by solving is negative , It means that the reference direction of current and voltage is opposite to the actual direction of current and voltage in the circuit . When a non associative reference direction is selected , If the value obtained from the solution is positive , It means that the actual current and voltage direction is opposite to the reference direction , If it's a negative sign , Then the actual direction is the same as the reference direction .

The meaning of the sign means voltage 、 The relationship between the actual direction of current and the reference direction .

（2） Comparison table 3-1、3-2 Theoretical value and measured data in , Observe whether there is error , And analyze the cause of the error .

answer ： Error . The reason for the error is that the voltmeter is not an ideal voltmeter , When the resistance value is too small, the shunt effect of the voltmeter will be obvious , Affect the measurement results . Again , Ammeter is not an ideal ammeter , When the resistance value is too large, the partial voltage effect of the ammeter will be obvious , Affect the measurement results . This produces errors .

（3） Calculation table 3-1 Medium ΣU And table 3-2 Medium ΣIA Is it zero ？ Why? ？

answer ： Calculation table 3-1 Medium ΣU And table 3-2 Medium ΣIA zero . This proves Kirchhoff's voltage law , That is, in any closed circuit , The algebraic sum of voltage drops on each element is equal to the algebraic sum of electromotive force . It also proves Kirchhoff's current law , That is, on any node in the circuit , At any moment , The sum of the current flowing into the node is equal to the sum of the current flowing out of the node .

Beginner circuit analysis , There may be mistakes , Also ask everybody not hesitate to grant instruction .

Due to the text , The relevant experimental projects in this paper cannot be shown , Resources have been uploaded , You can download it yourself .

Circuit analysis experiment of Shandong University 3 Verification of Kirchhoff's law in engineering documents - Other document resources -CSDN Download the circuit analysis experiment of Shandong University 3 Verification of Kirchhoff's law in engineering documents ：https://blog.csdn More download resources 、 For learning materials, please visit CSDN Download channel .