Charge redistribution on capacitors

In summary, the conversation discusses a circuit problem involving capacitors and a switch. Before the switch is closed, the charges on the capacitors are given, and after the switch is closed, the charges and energy in the circuit are discussed. The group discusses the energy supplied by the battery and the dissipation of heat in the wires. The conversation concludes with a correction to an incorrect statement and a statement of agreement that all options for the problem are correct.
  • #1
Jahnavi
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Homework Statement


capacitor.jpg


Homework Equations

The Attempt at a Solution


I will name the top left capacitor A , bottom left capacitor B and right capacitor C .

Before the switch is closed , charges on A and B will be 20 μC each and that on C will be 40 μC .

After the switch is closed ,both A and B will be shorted . Charge on C will be 60μC .

A and B will get discharged i.e there will be no charge on A and B .

On doing further calculations I am getting all four options correct .

The correct answer i.e incorrect statement is 3) .

But if charge on C changes from 40μC to 60μC , doesn't this mean 20 μC has flown through the battery and battery has done 0.6 mJ work or 0.6 mJ energy is supplied by the battery ?
 

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  • #2
Jahnavi said:
But if charge on C changes from 40μC to 60μC , doesn't this mean 20 μC has flown through the battery and battery has done 0.6 mJ work or 0.6 mJ energy is supplied by the battery ?
Find the total energy in the circuit before and after the switch is closed. The difference between the two energies would be the energy supplied by the battery.
 
  • #3
cnh1995 said:
Find the total energy in the circuit before and after the switch is closed. The difference between the two energies would be the energy supplied by the battery.

I don't think this is correct :smile:

You are forgetting energy dissipated as heat .
 
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  • #4
Also, the second option is confusing (or should I say 'tricky') because there is no resistance shown in the circuit. I'm afraid that makes this statement incorrect.
cnh1995 said:
The difference between the two energies would be the energy supplied by the battery.
Can you correct this statement?
Hint: The '1/2' in the equation for the energy stored in the capacitor.
 
  • #5
cnh1995 said:
Also, the second option is confusing (or should I say 'tricky') because there is no resistance shown in the circuit. I'm afraid that makes this statement incorrect.

It doesn't make a difference whether a resistance is shown in the circuit or not :smile: .

Heat is dissipated in the wires .
 
  • #6
Jahnavi said:
Heat is dissipated in the wires .
And the wires are shown to be ideal (although you can assume them to have some resistance).
 
  • #7
Anyways , I am finding all four options correct .

Which option do you find incorrect ?

Answer given is 3)
 
  • #8
Jahnavi said:
Anyways , I am finding all four options correct
Yes, I misread option C as 30mJ. I agree that all the options are correct.
(I still find dc capacitive circuits very tricky!).
 
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1. How does charge redistribution occur on capacitors?

Charge redistribution on capacitors occurs when there is a change in the voltage or current in the circuit. This causes a redistribution of charge between the plates of the capacitor, as electrons move from one plate to the other.

2. What is the purpose of charge redistribution on capacitors?

The purpose of charge redistribution on capacitors is to store and release electrical energy. As charge is redistributed, the capacitor builds up a potential difference, or voltage, between its plates. This stored energy can then be released to power electronic devices.

3. How does the capacitance of a capacitor affect charge redistribution?

Capacitance is a measure of a capacitor's ability to store charge. The higher the capacitance, the more charge can be stored on the capacitor's plates. This means that capacitors with higher capacitance will experience larger charge redistributions for the same change in voltage or current.

4. What factors can affect the rate of charge redistribution on capacitors?

The rate of charge redistribution on capacitors can be affected by factors such as the capacitance of the capacitor, the voltage or current in the circuit, and the resistance in the circuit. A higher capacitance or voltage, or a lower resistance, will generally result in a faster rate of charge redistribution.

5. How does charge redistribution on capacitors affect the overall circuit?

The process of charge redistribution on capacitors can affect the overall circuit in a few ways. First, it can lead to a time delay as the capacitor charges or discharges. Additionally, it can affect the stability of the circuit, as charge redistribution can cause fluctuations in the voltage. Finally, it can impact the overall energy efficiency of the circuit, as some energy may be lost in the form of heat during the process of charge redistribution.

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