A charge $q=10\mu C$ is distributed uniformly over the circumference of a ring of radius $3 m$ placed on $x-y$ plane with its centre at origin. Find the electric potential at a point $P(0,0,4m)$

 The electric potential at point $P$ would be

 $V=\frac{1}{4\pi {\epsilon }_0}·\frac{q}{r_0}$

Here,

$r_0=$ distance of point $P$ from the circumference of ring

$=\sqrt{{\left(3\right)}^2+{\left(4\right)}^2}=5m$

and $q=10\mu C={10}^{-5}C$

Substituting the values, we have

$V=\frac{\left(9.0\times {10}^9\right)\left({10}^{-5}\right)}{(5.0)}=1.8\times {10}^{4}V$