Millikan's oil drop experiment

1. Millikan’s Oil Drop Experiment(1909) Nathan Breidenbach Clemson University

2. What is the charge of an electron? Rutherford’s Gold Foil findings JJ Thompson’s discovery of an electron Charge/mass ratio known

3. video

5. Experimental E, applied electric field force W, weight of drop r, radius of drop n, viscosity of the air V1, terminal velocity when drop allowed to fall V2, terminal velocity when higher electric field causes drop to rise qE – W = 6πrnv2 = W * v2/v1

6. Results and Discussion Plate separation 0.016 m Voltage across the plates 5,085 V Distance of fall 1.021x10-2 m Viscosity of air 1.824x10-5 N s/m2 Density of oil 0.92x103 kg/m3 Density of air 1.2 kg/m3 Average time of fall (no field) 11.88 s Successive times of rise (with field) 1. 22.37 s 2. 34.80 s 3. 29.25 s 4. 19.70 s 5. 42.30 s

7. Conclusions Helped give more accurate values (ex: Avogadro’s Number) Controversy over data used Charge of electron has changed slightly since