Physics307L:People/Knockel/Notebook/070912

Millikan's oil drop experiment (charge of the electron)

Goal

I want to measure the charge of an electron by measuring the charge on a bunch of oil droplets and seeing if I can find that my calculated charges are integer multiples of some fundamental charge. The actual value is [math]\displaystyle{ e=1.60\times10^{-19} C }[/math].

Equipment

• power source (should go up to 500 V direct current)
• atomizer (to spray oil droplets)
• 2 multimeters
• banana cords
• banana plug patch cords
• DC transformer for light
• micrometer
• THE MILLIKAN DEVICE! (scope, viewing chamber, light, level, focusing wire, thermistor, etc.) (Model AP-8210 by PASCO scientific)

Setup

1. plug in power supply to wall and Millikan device (turned off)
2. hook up multimeter using banana plug patch cords to check voltage from power supply
3. level the Millikan device
4. plug in the light using DC transformer
5. focus viewing scope with focusing wire
6. aim the lamp/light/filament
7. turn on power supply and check it's voltage using first multimeter
8. attach another multimeter to the thermistor

Values (given to as many significant figures as are reasonably certain)

• [math]\displaystyle{ d=7.59\times 10^{-3} m }[/math] (plastic spacer width using micrometer)
• [math]\displaystyle{ \rho=8.86\times 10^2 \frac{kg}{m^3} }[/math] (density of oil given on bottle)
• [math]\displaystyle{ g=9.8 \frac{m}{s^2} }[/math] (gravitational acceleration)
• [math]\displaystyle{ p=8.5\times10^4 Pa }[/math] (air pressure in Albuquerque)
• [math]\displaystyle{ b=8.20\times10^{-3} Pa\cdot m }[/math] (some stupid constant)