Question

Find electrical potential due to Ring at a point P.  The point P is lies at distance Z from the origin along the Z- axis.

Answer 1

$$V=k\int r^{-1}dq\\V=k\int^{2\pi}_0\frac{\lambda Rd\theta}{\sqrt{z^2+R^2}}\\V=\frac{2\pi k\lambda R}{\sqrt{z^2+R^2}}\\ \\V=\frac{kq}{\sqrt{z^2+R^2}}$$