- #1

unscientific

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## Homework Statement

__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?

## 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