Q.
Three plates $A,B,C$ each of area $50cm^{2}$ have separation $3mm$ between $A$ and $B$ and $3mm$ between $B$ and $C.$ The energy stored when the plates are fully charged is
A) $1.6 \times 10^{- 9}\ J$
B) $2.1 \times 10^{- 9}\ J$
C) $5 \times 10^{- 9}\ J$
D) $7 \times 10^{- 9}\ J$
Explanation
(b) There are two capacitors parallel to each other
$\therefore$ Total capacitance $= \frac{2\varepsilon_{0}A}{d}$
$\therefore$ Energy stored $= \frac{1}{2}\left( \frac{2\varepsilon_{0}A}{d} \right)V^{2}$
$= \frac{8.86 \times 10^{- 12} \times 50 \times 10^{- 4} \times 12^{2}}{3 \times 10^{- 3}} = 2.1 \times 10^{- 9}\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.