A positive 20µC charge is placed at the centre of a circle of radius 20 cm. If we
move a positive 2µC charge once along the circumference of the circle, will any
work be done in the process? Justify your answer.
The work done
W=q(φ_1-φ_2 )
Here φ_1 is a potential of the electric field at initial point, φ_2 is a potential at final point.
Since the final point coincide with initial, we get
φ_1=φ_2
Finally
W=0