7) By what factor Velectric,f/Velectric.j will the potential difference across t

Question

7) By what factor Velectric,f/Velectric.j will the potential difference across the plates change if, once the capacitor was charged by the battery, it was disconnected from the battery while the area and separation were changed as above? (Express your answer to three significant figures.) Submit 8) By what factor Uelectric.f/Uclectric,i will the potential energy stored in the capacitor change if, once the capacitor was charged by the battery, it was disconnected from the battery while the area and separation were changed as above? (Express your answer to three significant figures.) Submit

Explanation / Answer

The capacitance of a parallel plate capacitor is given by:

C = epsilon0 A/d

When area becomes, A' = 5 A and d' = 1/5 d

C' = epsilon0 (5A)/(1/5)d = 25 epsilon0 A/d

C/C' = epsilon0 A/d x d/25 epsilon0 A = 1/25

C' = 25 C

Capacitance increases 25 times.

Q = CV

Since charge is directly proportional to C, charge will also increase 25 times.

V = Q/C ; Voltage will reduce by 25 times.

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