Answer to Question #115817 in Electricity and Magnetism for Ali

Question

The electric field produced by, a disk of radius R that carries uniformly distributed positive charge q, at a point P located on the axis of the disk (which we choose as the positive z- axis) a distance z from its center is given by equation;

E_z= 1/(4πε_0 ) 2qz/R^2 (1- z/√(z^2+R^2 ))
Starting with above equation write an equation in vector form that gives the electric field when point P is located either on the positive or negative axis of the disk of charge.

Answer 1

The electric field when point P is located either on the positive or negative axis of the disk of charge close to the disk in vector form is

$$\textbf{E}=\frac{q}{4\pi\epsilon_0z^2}\hat{\textbf{z}}.$$