Q. The capacity and the energy stored in a parallel plate condenser with air between its plates are respectively $C_{0}$ and $W_{0}.$ If the air is replaced by glass (dielectric constant = 5) between the plates, the capacity of the plates and the energy stored in it will respectively be
A) $5C_{0},\ 5W_{0}$
B) $5C_{0},\frac{W_{0}}{5}$
C) $\frac{C_{0}}{5},\ 5W_{0}$
D) $\frac{C_{0}}{5},\frac{W_{0}}{5}$
Explanation
(b) When a dielectric $K$ is introduced in a parallel plate condenser its capacity becomes $K$ times. Hence $C^{'} = 5C_{0}.$ Energy stored $W_{0} = \frac{q^{2}}{2C_{0}}$
$\therefore W^{'} = \frac{q^{2}}{2C'} = \frac{q^{2}}{2 \times {5C}_{0}} \Rightarrow W^{'} = \frac{W_{0}}{5}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.