(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, C increases to K times; V' = V/K
(iii) As E = V/d = and V is decreased; therefore, electric field decreases to 1/K times. 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