Principle of Millikan’s determination of the electronic charge, e

Question 1

Condition of Oil Drop

Answer 1

Charged oil drop placed between two charged plates.
Drop experiences an electrical force as it is in an electric field.

Question 2

If drop stationary (no electric field)

Answer 2

Electrical force is balanced by the gravitational force (mg)
Gravitational force acts downwards but is balanced by electrical force acting equal and opposite

Question 3

Derive Millikan Equation

Answer 3

F = mg E = V/d

EQ = mg

VQ/d = mg

Question 4

Stokes Law

Answer 4

There is a viscosity that acts on a body which is falling through a fluid

Question 5

Oil drop with no electric field equation

Answer 5

F = mg m = eV

Stokes law = mg
Use density equation and Volume of a sphere

9etavelocity/2densitygravitational acceleration

Question 6

Oil drop with electric field

Answer 6

Q = densityVol of sphereg*d/V

Question 7

Significance of Millikan’s Experiment

Answer 7

Experiment repeated multiple times and each time Q was a multiple of electron charge.

Charge is quantised and only appears in multiples of e.

Question 8

When P.D is Zero the droplet falls at…

Answer 8

Terminal speed