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Old Feb 8th 2016, 09:27 PM   #1
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Capacitors in a circut

http://m.imgur.com/zJOSzSZ

So I have this circut, and need to find the individual voltage and charge of each capacitor. I've been using Q=CV and tried treating the capacitors as both in series, and as 1 in parallel with 2 and 3. I'm not sure where I'm going wrong! There's a full description of the circut and variables with the image. Thank you!
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Old Feb 9th 2016, 07:47 AM   #2
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Well since you haven't posted your working I can't check on that.

But I can tell you that your approach is sound.

1) Assume that C1 charges fully to the 100 volts at switch position A.

2) This places CV = 15 x 100 = 1500 microcoulombs on C1

3) C2 and C3 do indeed form a series combination which I calculate can be replaced by a single 12 microfarad capacitor.

4) When the switch is thrown to position B the fixed charge, calculated above, is then distributed between the two capacitors in parallel (the 15 and 12 microfarads ie 27 microfarads) and the voltage changes to an unknown value, but must be equal to Q/C(parallel) which I make 1500/27 volts.

Last edited by studiot; Feb 9th 2016 at 01:40 PM.
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Old Feb 28th 2016, 08:45 PM   #3
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Originally Posted by studiot View Post
Well since you haven't posted your working I can't check on that.

But I can tell you that your approach is sound.

1) Assume that C1 charges fully to the 100 volts at switch position A.

2) This places CV = 15 x 100 = 1500 microcoulombs on C1

3) C2 and C3 do indeed form a series combination which I calculate can be replaced by a single 12 microfarad capacitor.

4) When the switch is thrown to position B the fixed charge, calculated above, is then distributed between the two capacitors in parallel (the 15 and 12 microfarads ie 27 microfarads) and the voltage changes to an unknown value, but must be equal to Q/C(parallel) which I make 1500/27 volts.

But when the switch is in position B, aren't all 3 capacitors in series? The battery is not connected so thats a dead end.
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Old Feb 19th 2017, 05:56 AM   #4
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1. C1 = 8.33x10^(-3) coulomb.

2. C2 = C3 = 0.666x10^-3 coulomb.


After switch is thrown to B. Simply use the method of same potential
i.e. V of C1 = V of C
(C= equivalent capacitance of C2 and C3 in series)


Sent from my Micromax AQ4502 using Tapatalk

Last edited by Soumyadip; Feb 19th 2017 at 06:01 AM.
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