User:Nathan Giannini/Notebook/Physics 307L/100913

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  • multimeter
  • Millikan Oil Drop Apparatus AP-8210
  • SMIEC Micrometer
  • TEL-Atomic 50V & 500V Supply
  • Robert Pharmaceutical Mineral Oil Intestinal Lubricant NDC 54092-417-06 (density = 886 kg/m^3)


  • Spacing between capacitors = 7.59-7.60mm

First Measure

  • Voltage reading (day 1)(i) - 499.9V
  • Voltage reading (day 1)(ii) - 501.3 V (adjusted to 500V)
  • Voltage Reading (day 2)(i) - 499.9 V
  • Voltage Reading (day 2)(ii) - 499.7 V
  • Resistance (day 1)(i) - 2.186 \cdot 10^{6} Ohms
  • Resistance (day 1)(ii) - 2.177 \cdot 10^{6} Ohms
  • Resistance (day 2)(i) - 2.233 \cdot 10^{6} Ohms
  • Resistance (day 2)(ii) - 1.990 \cdot 10^{6} Ohms
  • Temperature (day 1)(i) - 22 centigrade
  • Temperature (day 1)(ii) - 22 centigrade
  • Temperature (day 2)(i) - 20-21 centigrade
  • Temperature (day 2)(ii) - 25-26 centigrade
  • Viscosity (day 2)(i) - 1.826 \cdot 10^{-5} Nsm^-2
  • Viscosity (day 2)(ii) - 1.844 \cdot 10^{-5} NsM^-2
View/Edit Spreadsheet


  • Droplet 1: 3.3196 \cdot 10^{-17} C
  • Droplet 2: 6.7295 \cdot 10^{-16} C
  • Exposed Droplet: 4.7932 \cdot 10^{-16} C

Setting Up Our Equipment

We decided to use a box instead of a platform to put our apparatus on top of. This was a very effective solution for the height problem we were having, since we needed to look into the microscope.

Aligning The Optical System

By looking through the microscope while adjusting the incoming light, we were able to achieve a point where we could see the background while still seeing the needle as a bright, distinct line going from the the top to the bottom.

Adjusting and Measuring the Voltage

We used a multimeter (hand held) to measure the voltage we were putting between the capacitors.

Determining the Temperature

We measured the resistance of our system and from the reading we were able to determine the temperature using the temperature chart on our Millikan Apparatus.

The Experiment

On the first day we managed to see the droplets of our oil as point sources of light and to adjust our focus to get a better view of them, however, on the second day, that we were in this lab, we were unable to focus our reticule and adjust our light in such a way as to see our oil droplets. After 2 hours of adjusting, Prof. Koch focused the reticule for us and found an oil droplet in the lens of our capacitor divider. We also ended up needing to take off the cap on our capacitor in order for any drops to get in (we replaced the cap after we finished getting some droplets in).

Next, we started taking data on several droplets and found that the particles interacted with each other, lost mass, and sometimes spontaneously changed charge. All of these occurrences will cause error in our measurements.

Using the Thorium

We found that when we used the Thorium that is had almost no affect on our droplet. At most it barely changed the fall rate of the droplet.

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