thank you for your help!

my question is :how do you find the magnitude of the electric field that will balance the weight of an electron?

1 answer

You need to know the strength of the gravitational field where the electron is located. If it is in lab on Earth, the electron's weight is
W = m g

Set m*g = e*E and you get

E = g*(m/e)

The units will be N/C (or volts/meter) if e is 1.6*10^-19 Coulombs, and m is the electron mass, in kg

g = 9.8 m/s^2