Question

What is the magnitude of the electric field at a field point 2m from a point charge of 4nC

Answer 1

Given:

$r=2\:\rm m$

$q=4\:\rm nC=4*10^{-9}\: C$

$k=9*10^{9}\: \rm N\cdot m^2/C^2$

The electric field of a point charge is given by

$$E=k\frac{q}{r^2}=9*10^9*\frac{4*10^{-9}}{2^2}=9\:\rm N/C$$