A solid metallic sphere has a charge `+3Q`. Concentric with this sphere is a conducting spherical shell having charge `-Q`. The radius of the sphere is `a` and that of the spherical shell is `b(bgta)` What is the electric field at a distance `R(a lt R lt b)` from the centre

Options

A. `(Q)/(2pi epsilon_(0)R)`
B. `(3Q)/(2pi epsilon_(0)R)`
C. `(3Q)/(4pi epsilon_(0)R^(2))`
D. `(4Q)/(4pi epsilon_(0)R^(2))`

Answer

C

Explanation

Electric field at a distance `R` is only due to sphere because electric field due to shell inside it is always zero. Hence electric field `=(1)/(4piepsilon_(0)).(3Q)/(R^(2))`