Question

As shown in the figure below, a charge $+2C$ is situated at the origin $O$ and another charge $+5C$ is on the $x$-axis at the point $A$. The later charge from the point $A$ is then brought to a point $B$ on the $y$-axis. The work done is $\left(given\frac{1}{4\pi {\epsilon }_0}=9\times 10^{9}m/F\right)$

• A. $45\times 10^{9}J$
• B. $90\times 10^{9}J$
• C. Zero
• D. $-45\times 10^{9}J$

Answer 1

Answer: (C)

Work done $=U_f-U_i$
$=\frac{1}{4\pi {\epsilon }_0}\times 2\times 5\times \left(\frac{1}{2}-\frac{1}{2}\right)=0$