Question

A system consists of two charges $4\mu C$and $- 3\mu C$ with no external field placed at (-5 cm, 0,0) and (5 cm, 0, 0) respectively. The amount of work required to separate the two charges infinitely away from each other is

• A. $- 1.1J$
• B. 2 J
• C. 2.5 J
• D. 3 J

Answer 1

Answer: (A)

$- 1.1J$

Answer 2

: Here, $q_{1} = 4\mu C,q_{2} = - 3\mu C,r = 10cm = 0.1m$Electrostatic potential energy,

$U = \frac{1}{4\pi\varepsilon_{o}}\frac{q_{1}q_{2}}{r} = 9 \times 10^{9} \times \frac{4 \times 10^{- 6} \times ( - 3) \times 10^{- 6}}{0.1}$

$= - 1.1J$