JEE Main · 2007 · 29 Apr 2007 · Offline · Capacitance

WhatsApp Email

A parallel plate condenser with a dielectric of dielectric constant K between the plates has a capacity C and is charged to a potential V volts. The dielectric slab is slowly removed from between the plates and then reinserted. The net work done by the system in this process is

(A) $\frac{1}{2} (K - 1) C V^{2}$
(B) $C V^{2} (K - 1) / K$
(C) $(K - 1) C V^{2}$
(D)zero✓ Correct

Answer: (D)

Solution

Because the dielectric slab is drawn out slowly and then pushed back slowly while the plates stay connected to the same potential

V

, the capacitor is returned exactly to the condition it began in. Every slow, reversible step outward is undone by the matching step back inward, so the whole operation is a closed cycle. Over a cycle that restores the initial state the net work done by the system is zero.

JEE Main · 2007 · 29 Apr 2007 · Offline · Single correct option

Practise more: all JEE Main PYQs on Capacitance →

JEE Main · 2007 · 29 Apr 2007 · Offline · Capacitance

Solution

More JEE Main questions on Capacitance