Question

Two charged particles, with equal charges of 2.0 × 10⁻⁵ C, are brought from infinity to within a separation of 10 cm. Find the increase in the electric potential energy during the process.

Answer 1

Magnitude of charges, q₁ = q₂ = 2 × 10⁻⁵ C
Initial potential energy = 0
Each is brought from infinity to within a separation of 10 cm.
That is, r = 10 × 10⁻² m
So, increase in potential energy = final potential energy − initial potential energy.
That is, increase in potential energy, $∆U=\frac{1}{4\mathrm{\pi }{\epsilon }_0}\frac{q_1{q}_2}{r}$
$∆U=9\times {10}^9\times \frac{2\times {10}^{-5}\times 2\times {10}^{-5}}{10\times {10}^{-2}}=36\mathrm{J}$