The surface density of charge on a large vertical positively charged plate is ` sigma C* m ^ ( -2 ) `. A string attaches a metal ball of mass M and charge + q with the plate. Find out the angle between the string and the plate in equilibrium.

Explanation

Let the angle between the string and the plate in equilibrium ` = theta `
Tension in the string = T ,
Electric field at the position of the ball ` = E `
` = (sigma ) /( 2 in_ 0 ) `
In equilibrium ,
` T sin theta = q E = ( 9 sigma ) /( 2 in _ 0 ) , T cos theta = Mg `
` theta tan theta = ( q sigma ) /( 2in _ 0 Mg ) `
or, ` theta = tan ^( -1 ) (( qsigma )/( 2 in _ 0 Mg )) `