Question

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
( Capacitor is connected to the battery throughout)

• A. $\frac{1}{2}(K-1)C{V}^2$
• B. $C{V}^2(K-1)/K$
• C. $(K-1)C{V}^2$
• D. $0$

Answer 1

The correct option is D $0$

Since the capacitor is connected to the battery throughout the whole process, so the potential across the capacitor will remain same i.e V.

When the dielectric is removed and then reinserted, the final capacitance will as initial i.e C.

Thus, work done $W=U_f-U_i=\frac{1}{2}C{V}^2-\frac{1}{2}C{V}^2=0$