Question

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

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

Answer 1

Answer: (C)

zero

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