User:Manuel Franco Jr./Notebook/Physics Lab 307/2008/11/26
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SJK 15:05, 17 December 2008 (EST)
Millikan Oil Drop
Lab Partner: David
What to record:
The connections are simple. We adjust the height of the Millikan Drop apparatus, and leveled it using the level on the apparatus. Instead of using rods, we used three really big books to have it at eye level. I connected the power supply to an outlet, and connected the power supply and apparatus using the banana plugs. I also plugged the 12 V adapter to the halogen lamp. I connected the digital voltmeter to the thermistor connector as well.
We took the housing section of the apparatus apart, and measured the plastic plate separator in the housing. After measuring it, we cleaned inside the housing area, and reassembled it.
After making sure all the connections were fine, we turned on the power supply. The power supply was set at approximately 500 V. We then focused the viewing scope using the focusing wire by inserting the focusing wire on top of the capacitor plate. We also focused the halogen filament.
We measured the resistance and the voltage across the plate (see below). We were now ready to spray the oil with the atomizer in to the chamber. (Care! We squeezed the pump an nothing was visible on the screen. It was not until Aram told us that when you spray it there are two distinct sounds. One sounds like nothing but air, which is the one you don't want. And the second sound like something is coming out, which is the oil.) We then collected the data for the fall and rise times.
Data taken roughly at 3:41 PM (Mountain Time, DLST) on my cell phone clock.
"The definitions of the symbols used, in SI units:
Equation For Finding the Radius of the Oil Drop:
Equation For Finding the Mass of the Oil Drop:
Equation For Finding the Charge of the Oil Drop:
All derived equations can be found in the Lab Manual P.9
All of my data analysis is done in this excel sheet. E (Electric Field) is the voltage across the plastic plate over the space of the plate. We calculated E = 4.73 x 10^4 V/m. After calculating the radius, then the mass, and the charge of the oil drop, in the excel sheet, I multiply the charges by 1 X 10-19 for convenience of notation in the sheet. Also, in the sheet I group the values of the charges. This is done because charge is quantized at the atomic level. So there are clusters in the values. The groups are those clusters. Below in the picture I have taken the mean of those groups/clusters and graphed them based on their charge. The slope of this graph gives the experimental value of the electron.SJK 15:02, 17 December 2008 (EST)
My experimental value is 1.503(.069) x 10^-19 C.
I followed Jessy's data analysis format for this lab. I would like to give him the recognition of his work: Jessy's Data Analysis Excel Sheet. I would also like to thank Dr. Koch for the suggestion on my data analysis, and teaching David and I how to use the micrometer.