Calculate the voltage needed to balance an oil drop carrying 10 electrons between the plates of capacitor 5mm apart.The mass of the drop is 3x10-16kg and g=10ms-2.

We know that V/d=E

where V is voltage across the plates, d is the distance between the plates and E is the electric field.

10eE=mg where m is the mass of drop.

10eV/d=mg
=>V=mgd/10e
V=9.375 V

Approved