In figure below a charge Q is fixed. Another charge q is moved along a circular arc MN of radius r around it, from the point M to the point N such that the length of the arc MN = 1. The work done in this process is :
 

Options

A. zero
B. `(1)/(4piepsilon_(0)).(Qq)/(r^(2))l`
C. `(Qq)/(2epsilon_(0)r^(2))l`
D. `(Qq)/(2piepsilon_(0)r^(2))`

Answer

A

Explanation

Since the points M and N are at equal distances from point Q. So these will have same potential.
`V_(M)-V_(N)=0`
The work done in the process
`W=(V_(M)-V_(N))q=0`