Electric potential difference question

[jaejoon89]

Two parallel horizontal plates are 0.4 cm apart in air. An oil droplet of m = 4.9*10^-17 kg is introduced between the plates. If the drop has 2 electronic charges and if there is no air buoyancy, you can hold the droplet motionless between the plates if you keep the potential difference between them at...?



Do I use delta V = -int[E*dl] from a to b? How would I incorporate the mass?

 

[cepheid]

For your first question, yes, that is the definition of electric potential.

For your second question, the mass determines how much weight the electric field has to counteract.