Charges `+q` and `-q` are placed at points `A` and `B` respectively which are a distance `2L` apart, `C` is the midpoint between `A` and `B`. The work done in moving a charge `+Q` along the semicircle `CRD` is

Options

A. `(qQ)/(4pi epsilon_0L)`
B. `(qQ)/(2pi epsilon_0L)`
C. `(qQ)/(6pi epsilon_0L)`
D. `-(qQ)/(6pi epsilon_0L)`

Answer

D

Explanation

`W=Q[V_D-V_C]`
`V_D=(Kq)/(2L+L)-(Kq)/L=(Kq-3Kq)/(3L)=(-2Kq)/(3L)`
`V_C=0`
`W= (-KQqxx2)/(3L) = (-Qq)/(6piepsilon_0L)`