Consider a spherical shell of radius R wil a total charge +Q uniformly spread on its surface (centre of the shell lies at the origin x =0) Two point charge 1 and -q are brought, one after the other, from far away and placed at `x = -1//2` and `x = +a//2(a lt R)` respectively. Magnitude of the work done in this process is

Options

A. `(Q+q)^(2)//4 pi epsilon_(0)a`
B. `zero`
C. `q^(2)//4 pi epsilon_(0)a`
D. `Qq//4 pi epsilon_(0)a`

Answer

C

Explanation

`W_(1)=q((KQ)/(R))rArr W_(2)=((KQ)/(R)+(kq)/(a))(-q)`
`W-(-kq^(2))/(a)`