Question

In Millikan’s oil drop experiment, we make use of:
(A) Ohm’s law
(B) Ampere’s law
(C) Stokes law
(D) Faraday’s law

Answer 1

Hint: Robert Millikan in 1909 performed an experiment to determine the charge on an electron. For his work he received a Nobel Prize. The name of the experiment is Oil drop experiment. In the oil drop experiment Robert Millikan used charged oil droplets to determine the charge on the electron.

Complete step by step answer:
* To find the weight of the oil drop, Millikan allowed the oil drop to fall through the air in the oil drop experiment.
* Oil drop quickly reaches its terminal velocity and at this point, the weight of the drop is being balanced by the viscous effort of the air.
* The effort of the air can be calculated by using Stokes' Law, which endorsed Millikan to determine the weight of the drop.
Therefore Millikan used Stokes law in the oil drop experiment.

So, the correct option is C.

Additional information:
* Stokes law: The force that hinders a sphere while it moving via a viscous fluid is directly proportional to the velocity, the radius of the sphere and the viscosity of the particular fluid is called stokes law.
* Stokes law is used to calculate the viscosity of the given fluid.
Stokes law explains the following:
a) Floating of clouds
b) Bigger raindrops hurt us more than the smaller rain drops.
c) A man moving towards the earth with the parachute gains constant terminal velocity.

Note: Don’t be confused with the relation between viscosity and velocity. As the viscosity of the fluid increases the velocity to travel through the air decreases. Viscosity and velocity are inversely proportional to each other.