how will the (i) energy stored in the capacitor (ii) the electric field inside the capacitor be affected when it is completely filled with a dielectric material of dielectric constant 'K'?

 

When a dielectric medium is introduced in between the plates of capacitor with a battery connected across the plates :

(i) energy stored increases.

(ii) Electric field decreases

However , when battery across the plates of charged condensor is off:

i) energy stored decreases.

(ii) Electric field decreases