Question

3.
An oil drop of N excess electrons in held
stationary under a constant electric field E in
Millikan's oil drop experiment. The density of
the oil is p. Estimate the radius of the drop.​

Answer 1

Explanation:

Here n=10,E=3.65×10

4

NC

−1

,ρ

oil

=1.26gcm

−3

=1.26×10

3

kgm

−3

As the droplet is stationary, wheight of droplet = force due to electric field

or

3

4

πr

3

ρg=neE∴r

3

=

4πρg

3neE

∴r

3

=

4×3.14×1.26×10

3

×9.8

3×10×1.6×10

−19

×3.65×10

4

=1.13×10

−18

or r=(1.13×10

−18

)

1/3

=1.04×10

−6

m