Q. A variable condenser is permanently connected to a $100\ V$ battery. If the capacity is changed from$\ 2\mu\ F$ to $10\ \mu\ F,$ then change in energy is equal to
A) $2 \times 10^{- 2}\ J$
B) $2.5 \times 10^{- 2}\ J$
C) $3.5 \times 10^{- 2}J$
D) $4 \times 10^{- 2}\ J$
Explanation
(d) $\mathrm{\Delta}U = U_{2} - U_{1} = \frac{V^{2}}{2}(C_{2} - C_{1})$
$= \frac{(100)^{2}}{2}(10 - 2) \times 10^{- 6} = 4 \times 10^{- 2}\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.