(a)The attached figure shows the difference in behavior of conductor and dielectric in an electric field. In dielectric, there are no free charge carriers. A dipole moment is induced in the molecules of the dielectric on application of external electric field. The induced opposing field is not strong enough to completely cancel the external electric field. Hence, a reduced value of electric field exists inside the material of dielectrics (unlike conductors where net electric field inside is zero) (b)(i) Charge stored in the capacitor will not change as it is isolated by law of conservation of charge (ii) Electric field inside the plates is given by: E=Q/Aε₀ Since charge and area of cross-section does not change, electric field is also constant (iii) Energy stored in capacitor is U=Q²/2C=Q²d/2ε₀A Since d is doubled, stored energy is also doubled. Note that energy stored is provided by the external work done to increase the distance between the plates.