A vertical electric field of magnitude `4.00xx 10^5 NC^(-1)`. just prevents a water droplet of mass `1.000xx10^(-4) kg`from. falling., find the charge on the droplet.

Explanation

The forces acting on the droplet are
(i) the electric forces `q vec E` and
(ii) the force of gravity mg. To just prevent from falling, these two forces should be
equal and opposite. Thus,
`q (4.00xx 10^5 NC^(-1) = (1.00xx 10^(-4) kg ) xx ( 9.8 m s^(-2)`
or `q = 2.45 xx 10 ^9-9) C.`