In a circuit powered by a DC voltage source, three capacitors are connected in series and in parallel. What is the final voltage distribution?

深圳小花

In a circuit powered by a DC voltage source, three capacitors are connected in series and in parallel. What is the final voltage distribution? [Copy link]

 

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In a circuit powered by a 10V DC voltage source, there are three capacitors C1: 6nF C2: 2nF C3: 4nF. C2 and C3 are connected in parallel and then in series with C1. When the three capacitors are in the initial state, the voltage is 0. After the circuit enters the steady state, what is the voltage of each of the three capacitors? How to calculate it? Is there any relevant textbook? Thank you.

Teacher Chunyang , you have great skills, please feel free to give me some advice.

maychang

The solution is the same as your previous question.

Note that C2 and C3 are connected in parallel and can be treated as a 4uF capacitor. When the circuit reaches steady state, the current is zero, the amount of electricity charged into C1 is equal to the amount of electricity charged into C2+C3, and the sum of the voltage across C1 and the voltage across C2+C3 is 10V. Based on these two conditions, list the algebraic equation and solve it. Find the voltage across C2+C3, and the voltage across each capacitor is of course the voltage of the parallel capacitor.

maychang

It seems that you haven't figured out the previous problem (calculating the steady-state voltage of two capacitors when two capacitors and a resistor are connected in series).

maychang

It should even be said: You have not yet figured out what "capacitance" is, that is, you have not yet figured out the definition of "capacitance".

深圳小花

maychang posted on 2022-4-20 17:40 It should even be said: You haven't figured out what "capacitor" is, that is, you haven't figured out the definition of "capacitor". ...

Thank you very much. I wrote this question wrong. Please forgive me. I need to modify it and change C2:2nF C3:2nF to C2:2nF C3:4 nF

chunyang

Let me first ask whether there are relevant textbooks. Of course there are, such as junior high school physics and high school physics textbooks.

According to junior high school physics, the three capacitors are equivalent to two capacitors with capacities of 6nF and 4nF respectively connected in series. The answer is very simple. The voltage on the 6nF is 4V, and the voltage on the 4nF is 6V. The calculation formula is the resistance voltage divider formula, but the upper and lower parts must be swapped, that is, Uc1=(C2+C3/C1+C2+C3)*U.

Junior high school students only need to know how to calculate, but high school students should know why they calculate in that way.

High school physics taught us the definition and calculation formula of capacitance: C=Q/U, and the charge in a capacitor series circuit is equal everywhere, from which we can derive the calculation formula for junior high school.

maychang

Shenzhen Xiaohua posted on 2022-4-20 18:42 Thank you very much. I wrote this question wrong. Please forgive me. I need to modify it and change C2:2nF C3:2nF&n ...

NOTE: These capacitor values are independent of the solution. No matter how large these capacitors are, the solution is the same.

Questions that give numerical values are called arithmetic problems, and questions that use letters to represent numbers are called algebraic problems.

chunyang

When I was picking up a courier, the number was changed. Never mind, I won't change it. I'd like to clarify...

深圳小花

chunyang posted on 2022-4-20 18:58 During the time I was picking up the courier, the number was changed. Never mind, I won’t change it. I would like to make this clear…

If C2 and C3 are the same value, this problem is relatively simple. Can you tell me how to solve the problem when the capacitance of C2 and C3 is 2nF and 4nF respectively? Thank you very much.

chunyang

Shenzhen Xiaohua published on 2022-4-20 19:33 If C2 and C3 are the same value, this question is relatively simple. Can you tell me about the capacity value of C2 and C3?

In the time it takes to eat, you change the parameters and do second grade math problems? I understand the post on the 6th floor!

maychang

Shenzhen Xiaohua published on 2022-4-20 19:33 If C2 and C3 are the same value, this question is relatively simple. Can you tell me about the capacity value of C2 and C3?

"Can you tell me how to solve the problem when the capacitance of C2 and C3 is 2nF and 4nF respectively? Thank you very much."

I have already said in the 7th floor: Note: These capacitance values have nothing to do with the solution. No matter how large these capacitances are, the solution is the same.

maychang

Shenzhen Xiaohua published on 2022-4-20 19:33 If C2 and C3 are the same value, this question is relatively simple. Can you tell me about the capacity value of C2 and C3?

It seems that you didn't understand Chunyang's reply on the 6th floor, or even didn't read it at all. You probably didn't read my reply on the 7th floor either.

Alas!

Gen_X

I won’t participate.

深圳小花

maychang posted on 2022-4-20 18:58 Note: These capacitance values have nothing to do with the solution. No matter how large these capacitors are, the solution is the same. Questions that give numerical values are called arithmetic questions, ...

Thank you very much. I have read your reply. The current flowing through C1 is the same as the current flowing through the two capacitors C2/C3, but I don't understand how C2 and C3 distribute the current flowing from C1.

maychang

Shenzhen Xiaohua posted on 2022-4-21 15:54 Thank you very much. I have read your reply. The current flowing through C1 is the same as the current flowing through the two capacitors C2 / C3, but C2 C3 & ...

"The current flowing through C1 is the same as the current flowing through the two capacitors C2 and C3, but I don't understand how C2 and C3 distribute the current flowing from C1."

The voltages across C2 and C3 are equal, so the amount of electricity flowing through C1 must be distributed according to the capacity of the two capacitors. You can see this by simply writing out the definition of capacitor.

Chunyang has already written the definition of capacitance in the last line of his reply on the 6th floor: High school physics taught us the definition of capacitance and the calculation formula C=Q/U.

maychang

Shenzhen Xiaohua posted on 2022-4-21 15:54 Thank you very much. I have read your reply. The current flowing through C1 is the same as the current flowing through the two capacitors C2 / C3, but C2 C3 & ...

I said on the 12th floor: "It seems that you didn't understand Chunyang's reply on the 6th floor at all, or even didn't read it at all." I didn't wrongly accuse you.