(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Initial Conditions

(a)

Switch S_{2}kept open, switch S1 closed until C_{1}, C_{2}and C_{3}are fully charged. What is the potential difference across each capacitor? Now Switch S_{2}is closed. What is the new potential difference across each capacitor?

(b) Switches S_{1}and S_{2}are both closed. What is the p.d. across each capacitor?

3. The attempt at a solution

(a)

Before S_{2}is closed, p.d. across all 3 capacitors are the same:

V_{1}= V_{2}= V_{3}= 80V

V_{4}= 0V

After S_{2}is closed, capacitors 2 and 3 do not affect the circuit at all hence they retain the p.d. of 80V.

C_{1}distributes half of its charge to C_{4}.

V_{2}= V_{3}= 80V

C_{1}= C_{4}= 40V

(b)

C_{1}and C_{4}are in parallel, so C_{1,4}= 2C

thus it is C_{1,4}, C_{2}and C_{3}in series. Hence p.d. across each is:

V_{2}= V_{3}= 96V

V_{1,4}= V_{1}= V_{4}= 48V

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# Homework Help: Capacitance Circuit

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