Q. 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\ $volt. 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) $\frac{1}{2\ }(K - 1)CV^{2}$
B) $CV^{2}(K - 1)/K$
C) $(K - 1)CV^{2}$
D) Zero
Explanation
(d) On introduction and removal and again on introduction, the capacity and potential remain same. So, net work done by the system in this process
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ W = U_{f} - U_{i}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{1}{2}CV^{2} - \frac{1}{2\ }CV^{2} = 0$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.