Question

Two identical charges of 100 microcoulombs each are 12 cm apart. What is the electric potential at a point midway between them? What is the intensity of the electric field at the midway between them?

Answer 1

Potential

$V=V_1+V_2$

$V=\frac{kq_1}{r}+\frac{kq_2}{r}$

$$V=\frac{9\times10^{9}\times100\times10^{-6}}{0.06}+\frac{9\times10^{9}\times100\times10^{-6}}{0.06}=(15+15)\times10^6V$$

$V=30\times10^6V$

Electric field

At symmetry

$E=\frac{kq_1}{r^2}-\frac{kq_2}{r^2}$

$$E=\frac{9\times10^{9}\times100\times10^{-6}}{0.06^2}-\frac{9\times10^{9}\times100\times10^{-6}}{0.06^2}=(25-25)\times10^7V/m$$

$E_{net}=0V/m$