Suppose two parallel-plate capacitors have the same charge Q , but the area of c

Question

Suppose two parallel-plate capacitors have the same charge Q, but the area of capacitor 1 is Aand the area of capacitor 2 is 2A.

Part A

If the spacing between the plates, d, is the same in both capacitors, and the voltage across capacitor 1 is V, what is the voltage across capacitor 2?

Part B

If the spacing between the plates in capacitor 1 is d, what should the spacing between the plates in capacitor 2 be to make the capacitance of the two capacitors equal?

A d/2

B d

C 2d

D 4d

Explanation / Answer

Capacitance is proportional to Area/distance ------------------(1)
We also know Q = V*C (B) ------------------------(2)

A) from (1) we know capacitance of capacitor2 is twice that of capacitor 1, and from (2) we know voltage is inversly proportional to capacitance
so voltage across capacitor2 is V/2

B) from (1) we want 2A/x to be equal to A/d
thus x, the distance between the plates on capacitor2 must be 2d

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