Question

IN MILLIKAN OIL DROP EXPERIMENT WHY HIGHLY VISCOUS LIQUID IS USED INSTEAD OF LOW VISCOUS LIQUID?

Answer 1

Dear student

1) The Millikan's Oil drop experiment is an experiment used to determine the charge on an electron.

2) The oil droplets produced from an atomiser are allowed to enter in the upper plate of an electrical condenser through a tiny hole.

3) As these oil droplets fall down, their rate of fall is measured. From this the mass of each oil droplet is determined.

4) Next a beam of x ray is passed through the chamber. This ionises air present inside the chamber.

5) When the oil droplets (which are falling down) collide with the gaseous ions, they become charged.

6) The speed with which these oil droplets fall can be increased or decreased by applying different voltage. The drops can even stop falling at a certain voltage.

7) By carefully measuring the effect of electrical field strength on motion of oil droplets, it was found that magnitude of charge on each oil droplet is an integral multiple of charge q i.e q = ne [Where, q is the magnitude of electrical charge on the droplets, e is electrical charge, n = 1, 2, 3 …]

A highly viscous liquid is used because only a highly viscous liquid will collide with gaseous ions and become charged and allow different voltages to control the speed of the droplets.
In case the liquid is non-viscous these steps cannot be done as it will be freely flowing one.

Regards