Question

A conducting sphere of radius R, carrying charge Q, lies inside an uncharged conducting shell of radius 2R. If they are joined by a metal wire, then

• A. (A) Q/3 amount of charge will flow from the sphere to the shell
• B. (B) 2Q/3 amount of charge will flow from the sphere to the shell
• C. (C) Q amount of charge will flow from the sphere to the shell
• D. (D) K Q2/4R amount of heat will be produced

Answer 1

Answer: (D)

(D) K Q2/4R amount of heat will be produced

Answer 2

Explanation:
Capacitance of the capacitor (shell) having radius 2R,C2=4πε0(2R)Potential at surface of sphere, V1=14πε0QRPotential at the surface of the shell, V2=14πε0Q2RHence, sphere is at high potential and shell is at low potential. So, charge will flow from sphere to shell.Energy stored in C1,U1=Q22C1Energy stored in C2,U2=Q22C2Heat liberated isH=U1−U2=Q22[14πε0R−14πε0×2R]H=14πε0Q22R[1−12]=kQ24RHere, k=14πε0