User:David J Weiss/Notebook/notes Millikan Oil Drop

Millikan Oil Drop

In this lab we will be trying to determine by experimentation the value for the charge of an electron. We will do this by measuring how an oil drop with a negative charge responds to the force of gravity and the electric force applied through two charged plates.

Equipment

The equipment is as follows:

Millikan Oil Drop Apparatus (Pasco Scientific AP-8210)

Mineral Oil

SMIEC Micrometer

Multimeter (Wavetek 85XT)

500V DC Power supply (TEL-Atomic)

Atomizer

Stopwatch

Safety

The following are the safety concerns for this lab:

electrical safety. The main thing to keep in mind is that we are using electrical equipment to produce an electric field between the two plates and there is a danger of electrical shock

equipment safety. Don't do anything that could potentially cause harm to the equipment. Don't drop it for example because the main interment is one solid peace and could be severely damaged due to its solid construction.

Set Up

The set up is outlined in the operations manual for the Milkman Oil Drop Apparatus.

Notes

Day 1

• Worked with Elizabeth Allen
• Went through a safety brief with Dr. Koch and discussed whats going on in this lab
• used several books to get the height just right to view the eyepiece
• Set up the equipment and adjusted the eyepiece suing the focusing wire to get the grid into focus
• Hooked up the multimeter to the what ever to record the current and looked on the chart on the apparatus to find out at what temp that the experiment was being conducted and also found out what voltage is being applied to the capacitor plates
• Put some oil on the plates using the dropper and started to take data by picking out oil drops to watch
• Had some difficulty's in finding the drops and deiced to adjust the focus to find the drops I don't know if this will alter the data but I will calculate the calculations for the first day compared to how using a different way to find the drops on the other day
• Got some data but it was a struggle to find the drops

Day 2

• Worked with Elizabeth Allen again
• Came in and set up the lab. Took readings on the voltage across the plates which was 501.1 volts. We then took a temperature reading using the multimeter and the attached chart.
• Opened the ionization source lever to allow oil in the spray position and sprayed oil in the chamber.
• Having trouble seeing any drops again cleaned the apparatus where the oil is let in the chamber to try to see if there were any clogs that were preventing any of the oil from coming into the chamber.
• Seeing lots of drops but none of the drops appear on the grid I don't know why but since they are not on the grid I cannot tell where they are in relation and how far they travel in terms of the grid-lines. We got Dr Koch to help us with spraying and focusing the interment again. We started taking data on drops again.
• First try we could not find oil drops. Searched for them with the focus rings, but no luck. Re-calibrated the focus with the probe.and sprayed oil without the small black cover inside. Had Dr. Koch help us adjust the focus and found oil drops. Started to take data on how long a drop takes to fall across one grid line and how long it takes to rise with an applied voltage across the same distance. Took 9 different sets of data for different drops with multiple fall and rise times.

Day 3

• Worked with Elizabeth Allen
• came in and set up the equipment again, took reading on the voltage across the plates which was 501.1 volts. Then took a temperature reading on the multimeter and the chart.
• Let oil in using the sprayer. Found some drops to measure. Took data on 2 different drops both with multiple fall and rise times.

Data

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Errors

• some possible sources of error can come from the amount of drops inside the chamber so you can lose track of the drop your viewing and think that it is a different drop than it actually is. Another source could be when you open the ionization source lever to allow air to escape when you are putting the initial drops in the chamber and forget to close it allowing air to continue to flow in the chamber which could cause the drops to fall at a higher rate or lower rate.

References

Summary of the Millikan Oil Drop Lab

Milkman Oil drop experiment procedure procedure begins on page 7

David's Home

David's Notebook

Physics307L:Labs/Millikan