Q. Two identical capacitors each of capacitance 5$\mu$F are charged to potentials 2kV and 1kV respectively. Their –ve ends are connected together. When the +ve ends are also connected together, the loss of energy of the system is
A) 160 J
B) Zero
C) 5 J
D) 1.25 J
Explanation
(d) Loss of energy $= \frac{1}{2}\frac{C_{1}C_{2}}{(C_{1} + C_{2})}\ \left( V_{1} - V_{2} \right)^{2}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{1}{2}\frac{5 \times 10^{- 6} \times 5 \times 10^{- 6}(2000 - 1000)^{2}}{(5 + 5) \times 10^{- 6}}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \ \frac{5 \times 5}{2 \times 10} = 1.25J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.