Q. In the rectangle, shown below, the two corners have charges $q_{1} = 5\mu C$ and $q_{2} = + 2.0\mu C.$ The work done in moving a charge $+ 3.0\mu C$ from $B$ to $A$ is (take 1/4 $\pi\varepsilon_{0} = 10^{10}\ N - m^{2}/C^{2}$)

A) $2.8\ J$
B) $3.5\ J$
C) $4.5\ J$
D) $5.5\ J$
Explanation

(a) Work done $W = 3 \times 10^{- 6}\left( V_{A} - V_{B} \right);$ where
$V_{A} = 10^{10}\left\lbrack \frac{\left( - 5 \times 10^{- 6} \right)}{15 \times 10^{- 2}} + \frac{2 \times 10^{- 6}}{5 \times 10^{- 2}} \right\rbrack = \frac{1}{15} \times 10^{6}\ volt$
And $V_{B} = 10^{10}\left\lbrack \frac{\left( 2 \times 10^{- 6} \right)}{15 \times 10^{- 2}} + \frac{5 \times 10^{- 6}}{5 \times 10^{- 2}} \right\rbrack = - \frac{13}{15} \times 10^{6}\ volt$
$\therefore W = 3 \times 10^{- 6}\left\lbrack \frac{1}{15} \times 10^{6} - \left( - \frac{13}{15} \times 10^{6} \right) \right\rbrack = 2.8\ J$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.