A Charged particle of mass 1.0 g is suspended through a silk thread of length 40 cm in a horizantal electric field of `4.0 xx 10 ^4 NC ^(-1)` . If the particle stays aty a distance of 24 cm from the wall in equilibrium, find the charge on the particle.

Explanation

The situation is shown in (figure) The forces acting on the particle are (i) the force of fravity mg downward and (iii) the tension T along the thread. As the particle is at rest, these forces should add to zero Taking components along horizontal and vertical, `T cos theta = mg and T sin theta = F or, From the figure, sin theta = 24/40=3/5. Thus, tan theta = 3/4` . from (i) , `q(4.0 xx 10 ^NC ^(-1) = (1.0 xx 10 ^(-3) kg ) ( 9.8 ms ^(-2)3/4` . giving `q = 1.8 xx 10^(-7) C.`