Physics Help Forum Capacitors in a circut

 Electricity and Magnetism Electricity and Magnetism Physics Help Forum

 Feb 8th 2016, 09:27 PM #1 Junior Member   Join Date: Feb 2016 Posts: 1 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!
 Feb 9th 2016, 07:47 AM #2 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 995 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.
Feb 28th 2016, 08:45 PM   #3
Junior Member

Join Date: Dec 2015
Posts: 3
 Originally Posted by studiot 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.

 Feb 19th 2017, 05:56 AM #4 Junior Member   Join Date: Feb 2017 Posts: 7 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.

 Tags capacitors, circut, electricity

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post Samagra Thermodynamics and Fluid Mechanics 0 May 29th 2016 11:48 AM Clyner82 Advanced Electricity and Magnetism 0 Mar 28th 2016 10:05 AM binayakafle Electricity and Magnetism 18 Mar 1st 2010 08:30 AM Coobe Electricity and Magnetism 5 Dec 2nd 2009 09:24 AM nikhil Advanced Electricity and Magnetism 11 Jan 24th 2009 04:26 AM