A small conducting sphere of radius `r` is lying concentrically inside a bigger hollow conducting sphere of radius `R`. The bigger and smaller spheres are charged with `Q` and `q(Q gt q)` and are insulated from each other. The potential difference between the spheres will be

Options

A. `1/(4pi epsilon_0)(q/r-Q/R)`
B. `1/(4pi epsilon_0)(Q/R + q/r)`
C. `1/(4pi epsilon_0)(q/r + q/R)`
D. `1/(4pi epsilon_0)(q/R - Q/r)`

Answer

C

Explanation

Potential at A
`V_A=(KQ)/R +(Kq)/R`
Potential at B
`V_B = (KQ)/R +(Kq)/r`
`V_B -V_A =K [q/r -q/R]`