Question

Each plate of a parallel plate capacitor has a charge q on it. The capacitor is now connected to a batter. Now,
(a) the facing surfaces of the capacitor have equal and opposite charges
(b) the two plates of the capacitor have equal and opposite charges
(c) the battery supplies equal and opposite charges to the two plates
(d) the outer surfaces of the plates have equal charges

Answer 1

(a) The capacitor’s facing surfaces have opposite and equal charges  

(b) The capacitor’s two plates have opposite and equal charges  

(d) The plates’ outer surfaces have equal charges  

Explanation:

$\mathrm{q}-\mathrm{Q}=\mathrm{q}+\mathrm{Q} \rightarrow \mathrm{Q}=0$

• Please note, option (c) is incorrect the reason being why is that the battery is a source of energy not charge.
• If a capacitor plates have equal charge on outside and equal charge on inside, then one can think that the charge on the plates must be equal so option (b) cannot be incorrect.