Question

The electric field at a point due to a point charge is $30N/C$ and the electric potential at that point is $15J/C$ respectively. What is the distance of the point from the charge and the magnitude of the charge?

Answer 1

For point charge

$E=V/r$

Given

$V=15J/C$

$E=30N/C$

Distance from point charge, r=?

Point charge, q=?

$r=V/E=15/30=0.5m$

$V=\frac{q}{4\pi {\epsilon }_{0}r}$

$q=4\pi {\epsilon }_{0}rV$

$q=\frac{1}{9\times {10}^9}\times 0.5\times 15$

$q=0.83\times {10}^{-9}C$

$q=0.83nC$