The point charge `q` is within the cavity of an electrically neutral conducting shell whose outer surface has spherical shape. Find the potential `V` at a point `P` lying outside the shell at distance `r` from the center `O` of the outer sphere.
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Options

A. `V = (1)/(4 pi epsilon_0) q/( r)`
B. `V = (1)/(2 pi epsilon_0) q/( r)`
C. `V = (1)/(pi epsilon_0) q/( r)`
D. `V = (3)/(4 pi epsilon_0) q/( r)`

Answer

A

Explanation

A negatively charge `-q` will be induced on the inner surface of cavity and positive charge `+q` will be induced on the outer surface, which will be uniformly distributed. There will be no field or potential at point `P` due to inner charges `+q and -q`. Potential at `P` will only be due to outer `+q` charges. So
`V_P = (1)/(4 pi epsilon_0) q/r`
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