Question

Derive an equation for the energy stored in a capacitor. If a dielectric is introduced between the plates how will energy change?

Answer 1

Derivation doesn't change till you get

W = Q² /2C

Q = A x sigma

C = d/A x epsilon 0

therefore

E = (sigma)² d/ 2 epsilon 0

but E = sigma / epsilon 0

So

Energy = epsilon 0 x E² x A x d/2

If you use medium with dielectric constant k,

epsilon = k . epsilon 0

hope it is help full and mark me as brain list

So,

E = k. epsilon 0 x E²  x A x d/