Question

In a parallel plate capacitor length l and width b are 3 cm and 1 cm respectively. Separation between plates d is \(3\ \mu m\). By which of the following values capacitance increases by a factor of 10.

(A) \( l = 6 \ cm, \ b = 5 \ cm, \ d = 3 \ \mu m\)

(B) \(l = 5\ cm, \ b = 2 \ cm, \ d = 1\ \mu m\)

(C) \(l = 5\ cm, \ b = 1 \ cm, \ d = 30\ \mu m\)

(D) \(l = 1\ cm,\ b = 1 \ cm,\ d = 30\ \mu m\) 

(1) A, B

(2) A, C

(3) B, C

(4) B, C, D

Answer 1

Correct option is : (1) A, B

\(C = \frac{A\varepsilon _0}{d}\)

\(C = \frac{Ib \varepsilon _0}{d}\)

\(C_i =\frac{3\times 3}{3} \varepsilon _0 \times 10^2 = 10^2 \varepsilon _0\)