A parallel plate capacitor as a uniform electric field E in the space between the plates. If the distance between the plates is d and area of each plate is A, the energy stored in the capacitor is:

Options

(a) 1/2 ?￢ﾂﾀ E²
(b) E² Ad / ?￢ﾂﾀ
(c) 1/2 ?￢ﾂﾀ E² Ad
(d) ?￢ﾂﾀ E Ad

Correct Answer:

1/2 ?￢ﾂﾀ E² Ad

Explanation:

The energy stored by capacitor U = 1/2 CV²
…(i)
V is the p.d. between two plates of the capacitor.
The capacitance of the parallel plate capacitor V = E.d. C = A ?￢ﾂﾀ / d
Substituting the value of C in equation (i)
U = 1/2 A ?￢ﾂﾀ / d (Ed)²
= 1/2 ?￢ﾂﾀ E² Ad