Q 1.25: An oil drop of 12 excess electrons is held stationary under a constant electric field of (Millikan’s oil drop experiment). The density of the oil is 1.26 g cm-3. Estimate the radius of the drop.
The force due to the electric field is balancing the weight of the oil droplet.
Weight of the oil drop = Densityx Volume of the droplet x g =
Force due to the electric field = E x q
Charge on the droplet, q = No. of excess electrons x Charge of an electron =
Putting known and calculated values: