Question

A solid conducting sphere of radius 10 cm is enclosed by a thin metallic shell of radius 20 cm. A charge $q=20\mu C$ is given to the inner sphere. Find the heat generated in the process when the inner sphere is connected to the shell by a conducting wire

• A. Zero
• B. 24 J
• C. 9 J
• D. 12 J

Answer 1

The correct option is C

9 J

On connecting, the entire amount of charge will shift to the outer sphere. Heat generated

$U_i-U_f=\frac{q^2}{8\pi {ϵ}_0{R}_1}-\frac{q^2}{8\pi {ϵ}_0{R}_2}$

$=\frac{(20\times {10}^{-6})\times 9\times {10}^9}{2}[\frac{1}{0.10}-\frac{1}{0.20}]=9J$