A very large sphere having charge `Q` uniformly distributed on the surface s compressed uniformly till its radius reduces to `R`. The work done by the electric force in this process is :

Options

A. `(Q^(2))/(8pi in_(0)R)`
B. `(-Q^(2))/(8pi in_(0)R)`
C. `oo`
D. `0`

Answer

B

Explanation

`(W_(AB))` electric force `= U_(A) - U_(B) = 0 - (KQ^(2))/(2R) = (-Q^(2))/(8pi epsilon_(0)R)`
[`:' UA = 0` as sphere is large]