Millikan Oil Drop

Timed distance = 3.0x10 -4 m
Viscosity of air = 1.82x10 -5 Ns/m 2 at 20°C
Density of air = 1.29 kg/m 3
Density of oil = 9.67x10 2 kg/m 3
Atmospheric Pressure of air = 76.1 cm Hg
Gravitational Acceleration (g) = 9.81 m/s 2
Calculate value of K
= 1.05x10 -10 SI Units
Ancillary Data
Plate separation measurement
Mass of S.G. Bottle
Mass of S.G. Bottle & Water
Mass of S.G. Bottle & Oil
Static experiment
Drop # t g (avg) V s
1-5 In film In film
6 10.05 s 82 V
7 3.48 s 150 V
8 2.35 s 170 V
9 5.24 s 111 V
10 8.99 s 53 V
1 st reading: 122.07 mm
2 nd reading: 118.77 mm
17.396 g
41.572 g
40.776 g
Dynamic Experiments
Drop # t g (avg) t f (avg) V
1-4 In film In film in film
5 2.78 s 32.00 s 324 V
6 10.05 s 9.10 s 178 V
7 3.48 s 7.23 s 222 V
8 2.35 s 6.91 s 233 V
9 5.24 s 9.75 s 180 V
10 5.27 s 15.10 s 330 V
Conclusions
The calculated values of e’, even without Stokes’ law correction, will show that, if
the average lowest values of e’ are divided into the significantly larger values, the larger
values will be approximately simple multiples of the lowest value. Therefore, the
average lowest value corresponds to the fundamental unit charge e. The accurate value
for e within the experimental errors can be found by applying the Stokes’ law correction
to the results.
Student Activities: Student should be prepared to note for themselves the readings for the
first 5 static experiments and the first 4 dynamic experiments. A stopwatch will be
necessary.