A charge of 6 μC is located 18 cm away from a point P. The work done in bringing a charge of 3 nC from infinity to the point P is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 9 x 10−4 J
The work done in bringing a charge q from infinity to a point equals q times the electrostatic potential there.
\( \displaystyle V_P = \frac{1}{4\pi\varepsilon_0}\,\frac{Q}{r} = \frac{9\times10^{9} \times 6\times10^{-6}}{0.18}\,\mathrm{V} = 3\times10^{5}\,\mathrm{V} \)
\( \displaystyle W = qV_P = 3\times10^{-9}\,\mathrm{C} \times 3\times10^{5}\,\mathrm{V} = 9\times10^{-4}\,\mathrm{J} \)