Question

"A droplet of oil carries an extra charge of one electron and is held motionless between parallel plates separated by 1.80 cm across which there is a potential difference of 55.5 kV. What is the mass of the droplet?"

I assumed that this whole thing was actually a vertically placed capacitor.

Here is my approach on this:

A free body diagram shows that:

Fg = Fe

mg = qE

mg = qV/d

Thus m = qV/(dg)

Plugging in values : m = (1.6 * 10-19 * 55500)/(0.018 * 9.8)

I find m = 5.04e-14 kg. This is incorrect. Where did I go wrong?

Answer 1

Looks right to me.