(a) Obtain the expression for the energy stored per unit volume in a charged parallel plate capacitor. (b) The electric field inside a parallel plate capacitor is E. Find the amount of work done in moving a charge q over a closed rectangular loop abcda.

(a)Energy stored in a capacitor is given by: E=1/2CV²
Using C=ε₀A/d
E=1/2(ε₀A/d)V²
Using potential gradient, E=V/d
E=1/2ε₀AE²d
E/Ad = 1/2ε₀E²
The term on the left hand side is the energy stored per unit volume in a capacitor
(b)As electric field is conservative, net work done by electric force in moving a charge through a loop is zero.