What Charge Is A Spherical Drop? Parallel Plates, stuck on physics past paper question!

Hi there,

I am working through a past paper for physics from home and I am very stuck on the following question, is anybody able to shed any light on it for me?

It's worth 9 marks.

Thank you in advance.




Q. Two parallel plates are placed 0.10m apart with one vertically above the other and their edges aligned. The potential difference of the upper plate is 100kV relative to the lower plate. What charge must be a spherical raindrop of diameter 1.0mm carry if it remains suspended between the plates? Assume that the electric field between the plates is uniform and give your answer in units of the charge on an electron. (The density of the water is 1000 kg m-3.)

You would have to start working out the mass of the raindrop

The force of gravity depends on mass. and that must be balanced by the electrical forces.

You must have some equations to work with?