A parallel plate capacitor is charged to a potential difference V by a dc source. The capacitor is then disconnected from the source. If the distance between the plates in doubled, state with reason how the following will change,
(i) electric field between the plates,
(ii) capacitance and
(iii) energy stored in the capacitor.

Options

A. only (i) and (ii)
B. only (i) and (iii)
C. only (ii) and (iii)
D. All (i),(ii) and (iii)

Answer

A

Explanation

The charge of the plates cannot change because the plates are isolated. Inserting the dielectric changes the capacitance and therefore changes the potential difference (from V=Q/C), since the charge is fixed.