(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 loop a b c d a.(a) Consider a parallel-plate capacitor of plate area A.
Let us say, charge Q is given to the capacitor. Now, in order to increase the separation between the plates, plate b is slowly pulled away from plate a.
Distance between the two capacitor plates = d
Force on plate b due to plate a is given by,
Work done inorder to displace the plate from its fixed position is, W=Fd
; where is the capacitance of the capacitor.
Work done is equal to increase in energy of the system.
Electric field is created in a volume which is given by, V = Ad
So, Energy stored per unit volume is given by,
where, E is the intensity of the electric field.
(b) Work done, W= F.d ;
where, F is the force exerted on electrical charge and d is the displacement.
Since, the charge is moved along a closed path, net displacement is zero.
Therefore, work done= 0