# pre-charged capacitors

1. ## pre-charged capacitors

Hi,
I am facing a prblem in analyzing this circuit intuitively. Circuit is as follows:
there are 3 capacitors 4C ,2C, 1C which are pre-chharged at 1V,2V and 5V respectively. then they are connected as shown in the figure:   Reply With Quote

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2. ## Re: pre-charged capacitors

The diagram is a bit vague, you have a ground symbol at the bottom, but where is the top connected to?

Do you mean all capacitors are connected in parallel?  Reply With Quote

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3. ## Re: pre-charged capacitors Originally Posted by FvM The diagram is a bit vague, you have a ground symbol at the bottom, but where is the top connected to?

Do you mean all capacitors are connected in parallel?
NO,the top is connected to 10v battery. and we need to know the transient response when these capacitors are connected as shown in figure.  Reply With Quote

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4. ## Re: pre-charged capacitors

You can calculate recharge and effect of 10V source separately (superposition). For the former use conservation of charge, the latter is a simple voltage divider.  Reply With Quote

5. ## Re: pre-charged capacitors

C2 and C3 are in parallel. They must have the same voltage.
If they are charged as noted, 3V and 5V, as soon as you connect them,
The charges will re-distribute so that both have the same voltage and q2 = c2 * V and q3 = 3 * V
When this happens, the current is limited only by the resistance of the wires.

The schematic shows 3V and 5V, while the text says 2V and 5V ?

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Conceptually:
C2 and C3 are effectively 1 capacitor. he parallel resistor will discharge the parallel combination of C2 and C3 until there is 0 V across them,
and hence 0V across the resistor.
Meanwhile, the voltage on C1 will rise to 10 V, and current will stop flowing.
So, after a long time, there will be no current flowing, C1 will be at 10 V, and C2, C3 and R will have 0V across them.  Reply With Quote

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6. ## Re: pre-charged capacitors Originally Posted by Akshaay Hi,
I am facing a prblem in analyzing this circuit intuitively. Circuit is as follows:
there are 3 capacitors 4C ,2C, 1C which are pre-chharged at 1V,2V and 5V respectively. then they are connected as shown in the figure: What if the top terminal of 4c capacitor is left open?(i.e if there is no 10v source on the top of 4c) what will be the transient response then?  Reply With Quote

7. ## Re: pre-charged capacitors

C2 and C3 will eventually discharge through the resistor.
Nothing will happen to C1 since it is open circuit.  Reply With Quote

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