Question

As shown in the figure below, a charge $+2\,C$ is situated at the origin $O$ and another charge $+5\,C$ 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 $\left( given \frac{1}{4\pi\varepsilon_{0}} = 9×10^{9} m/F\right)$

• A. $45 × 10^9 \,J$
• B. $90 × 10^9\, J$
• C. Zero
• D. $- 45 × 10^9 \, J$

Answer 1

Answer: (C)

Work done $=U_{f}-U_{i} $
$=\frac{1}{4 \pi \varepsilon_{0}} \times 2 \times 5 \times\left(\frac{1}{2}-\frac{1}{2}\right)=0$