Suspending a Charged Droplet: Electric Field E Found by Millikan

[4real4sure]

Homework Statement

A spherical droplet of radius R and effective mass density ρ. carries a total charge q in a gravity field g. What electric field E iz, will suspend the charged droplet? Millikan found by this method that all droplets carried integer multiples ofnegative charge e= -1.6 x 10-coul.

Homework Equations

F=ma

The Attempt at a Solution

I would like to confirm if my attempt is okay or not. Please can you give explanation based on whatever method it is required to be solved in.

q E = ρ g (4/3) ∏ R³

E = ((ρ g)/q) (4/3) ∏ R³

 

[cepheid]

Homework Statement

A spherical droplet of radius R and effective mass density ρ. carries a total charge q in a gravity field g. What electric field E iz, will suspend the charged droplet? Millikan found by this method that all droplets carried integer multiples ofnegative charge e= -1.6 x 10-coul.

Homework Equations

F=ma

The Attempt at a Solution

I would like to confirm if my attempt is okay or not. Please can you give explanation based on whatever method it is required to be solved in.

q E = ρ g (4/3) ∏ R³

E = ((ρ g)/q) (4/3) ∏ R³

It makes sense to me. You equated the gravitational force to the electric force (in magnitude). You computed the mass by multiplying the density by the volume. I don't see any problems.