There are two equipotential surface as shown in figure. The distance between them is r. The charge of ?q coulomb is taken from the surface A to B, the resultant work done will be [MP PMT 1986; CPMT 1986, 88]

• A.                    \[W=\frac{1}{4\pi {{\varepsilon }_{o}}}\frac{q}{r}\]
• B.                    \[W=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{q}{{{r}^{2}}}\]
• C.                    \[W=-\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{q}{{{r}^{2}}}\]
• D.                    W = zero