Question

A metallic sphere has a charge of $10\mu C$. A unit negative charge is brought from $A$ to $B$ both $100cm$ away from the sphere but $A$ being east of it while $B$ being on west. The net work done is:

• A. Zero
• B. $2/10joule$
• C. $-2/10joule$
• D. $-1/10joule$

Answer 1

The correct option is A Zero

According to question,

Work done $=W$ (Change in potential energy )

$W=U_f-U_i$

$U_i=\frac{1}{4\pi C}\frac{1\times 10\times {10}^{-6}}{1}$ ($U_i$ is the initial potential energy when unit is lying east)

$U_f=\frac{1}{4\pi C}\frac{1\times 10\times {10}^{-6}}{1}$ ($U_f$ is the final potential energy when unit is lying west)

$W=\frac{1}{4\pi C}\frac{1\times 10\times {10}^{-6}}{1}-\frac{1}{4\pi C}\frac{1\times 10\times {10}^{-6}}{1}$

$=0$

$W=0$