An oil drop of 12 excess electrons is held stationaty under a constant electric field of `2.55xx10^(4) NC^(-1)` in Millikan's oil drop experiment. The density of the oil is `1.26 g cm^(-3)`. Estimate the radius of the drop. `(g = 9.81 ms^(-2) , e = 1.60xx10^(19) C)`

Explanation

(a) The field lines showed in (a) do not represent electrostatic field lines because field lines must be normal to the surface of the conductor.
(b) The field lines showed in (b) do not represent electrostatic field lines because the field lines cannot emerge from a negative charge and cannot terminate at a positive charge.
(c) The field lines showed in (c) represent electrostatic field lines. This is because the field lines emerge from the positive charges and repel each other.
(d) The field lines showed in (d) do not represent electrostatic field lines because the field lines should not intersect each other.
(e) The field lines showed in (e) do not represent electrostatic field lines because closed loops are not formed in the area between the field lines.