Question

σ is the uniform charge density present on the surface of a semi sphere of radius R. what is the electric potential at the centre?

Answer 1

The given answer is mg/q.

When the oil drop is falling freely due to the effect of gravity at various medium with terminal speed v, then it is given as mg = 6πηrv.

To move the oil drop upward with terminal velocity v if E is the electric field intensity applied, then Eq = mg + 6πηrv = mg + mg = 2mg.

So, E = 2 mg/q.