Deduce an expression for the electrostatic energy stored in a capacitance 'C' and having charge Q
How will the electric field inside capacitor be affected when it is completely filled with a dielectric material of dielectric constant K ?

Explanation

The original electric field inside capacitor `E = (sigma)/(in_(0)) = (Q)/(A in_(0))`
On introducing dielectric new electric field `E. = (sigma)/(K in_(0)) = (Q)/(K A in_(0)) = (E)/(K)`
Thus on introducing the dielectric , both energy stored and electric field are reduced by a factor .