Question

Supposed a charge is at the origin

Determine the direction angle of the electric field at the point( 0.9, 1.2) measured counterclockwise from the positive x axis if the particle is positively charged?

Answer 1

The electric field compotents

$$E_x=k\frac{q}{(\sqrt{x^2+y^2})^3}x$$

$$E_y=k\frac{q}{(\sqrt{x^2+y^2})^3}y$$

Hence,

$$\tan\theta=\frac{E_y}{E_x}=\frac{y}{x}=\frac{1.2}{0.9}=1.33$$

$$\theta=\tan^{-1}1.33=53^{\circ}$$