Figure shows some equipotential lines distributed in space. A charged object is moved from point `A` to point `5`.

Options

A. The work done in Fig. (i) is the greatest.
B. The work done in Fig. (ii) is least.
C. The work done is the same in Fig. (i), Fig. (ii) and Fig. (iii).
D. The work done in Fig. (iii) is greater than Fig. (ii) but equal to that in Fig. (i).

Answer

C

Explanation

Work done by an external agent in moving a charge q from point A towards point B is given by,
`W=q(V_(B)-V_(A))`
For all the three figures, `V_(B)=40V` and `V_(A)=20V`. Thus, the work done by the external agent will be:
`W=q(40-20)=20q`, i.e. same in all the three cases.