Question
Physics Question on electrostatic potential and capacitance
1000 similar electrified rain drops merge together into one drop so that their total charge remains unchanged. The electric energy gets increased by
A
100 times
B
200 times
C
300 times
D
400 times
Answer
100 times
Explanation
Solution
Let q be charge on each small drop of radius r. If R is radius of big drop, then
34πR3=1000×34πr3
∴R=10r
and C′=10C
Initial energy, E1=1000×2Cq2
Final energy, E2=2C′(1000q)2
E1E2=C′1000×C=1000×101=100