(i) The capacitance of capacitor increases to K times (since C = (Kε0A)/d ∝ K)
(ii) The potential difference between the plates becomes 1/K times.
Reason: V = Q/C;Q same, increases to K times
∴ V' = V/K
As E = V/d = and V is decreased; therefore, electric field decreases to 1/K times.
(iii) Energy stored by the capacitor, u =Q2/2C.
As Q = constant, C is increased, and so energy stored by capacitor decreases to 1/K times.