Question

A charge of $20\mu C$ produces an electric field. Two points are $10cm$ and $5cm$ away from this charge. Find the values of potentials at these points and also find the amount of work done to take an electron from one point to the other.

Answer 1

$V_A=\frac{1}{4\pi {ϵ}_0}\frac{q}{r_A}=\frac{9\times {10}^9\times 20\times {10}^{-6}}{0.05}$

$V_A=36\times {10}^{-5}V$

$V_B=\frac{1}{4\pi {ϵ}_0}\frac{q}{r_B}=\frac{9\times {10}^9\times 20\times {10}^{-6}}{0.1}$

$V_B=18\times {10}^{-5}V$

$\text{Work done}=e△V$

$W=1.6\times {10}^{-19}(36\times {10}^{-5}-18\times {10}^{-5})$

$W=28.8\times {10}^{-24}j=0.18meV$