User:Darrell Bonn/Notebook/307L Lab book/lab 5 Millikan

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Contents

Procedure

Equipment setup

  1. Measuring the thickness of the plastic between the plates. D for capacitor: 7.75mm, 7.76 on other side
  2. Cleaned capacitor with dry paper towel, took care to remove any particles
  3. Placed the focusing wire in place, connected light and focused on the wire
  4. Adjusted the light to best illuminate the wire exactly as explained in manual. Removed the focusing wire.
  5. There are 5 small divisions per large division in the viewer grid
  6. Attached 500 volt power supply.

The procedure can be found online at Pasco's website

density of Squib#5597 Mineral Oil given by manual is 886kg/m^3

Measurements
Time measurements are between two major lines
Initial Trials – We took a bit of time to simply play with the tools to be sure we understood what we were doing.
Barometric pressure: 30.41 in / 1029.7 hPa (from http://www.wunderground.com/US/NM/Albuquerque.html)
Measured 500.8 V on the capacitor
Temperature within the chamber 26C
Added droplets with a single squeeze of the atomizer. Immediately saw drops within the viewer. Picked a small, slow moving one and timed it.
Picked a drop, Setting top plate positive, it went up

Data Acquisition

Time data for drop movement is recorded in seconds, no units are put in below to make data easier to copy and paste into other applicatoins
Data is also recorded sequentially instead of in a table so that precise time of the temperature readings can be seen
Procedure is for one person to watch the drop and control the aparatus, calling out to the next person who has the stop watch. The person with the stop watch records the time in the "lab book". There is some inherent human error in this method, but it seems to be the best we can do with the tools on hand. A good stop watch that records consecutive times would be very helpful to improve accuracy and to speed up acquisition process.

It is very tiring watching these drops. Setting the aparatus to a comfortable height is essential as this is a lengthy process and discomfort inhibits good, patient data acquisision. A better sheild around the eye piece would also help. Or better yet, one of those CCD adapters that can project the image to a computer screen.

Day One

Drop 1

  • Up under positive charge on top plate: 4.33, 4.10, 4.27
  • Down with both plates grounded: 17.56, 19.24
  • Down with charge on bottom plate:

Lost drop to view

Drop 2

  • Up under positive charge on top plate: 13.12 17.46 11.27 12.55 11.58
  • Down with both plates grounded: 18.17 19.46 19.86
  • Down with charge on bottom plate:

Drop 3

  • Up under positive charge on top plate: 8.62, 7.36, 7.55
  • Down with plates grounded: 23.08, 26.5, 26.98
  • Down with negative charge on top plate:


Measured temperature: 27C

Drop 4

  • Up under positive charge on top plate: 2.24s, 2.56s, 2.37s
  • Down with plates grounded: 7.17s, 6.46s, 6.81s
  • Down with negative charge on top plate:


Tried for about 10 minutes to change the charge on this drop. No joy.

Day Two

Once we find a candidate and get a few measurements, we will open the ionization source in hopes of getting at least a few of these to change charge.

  • Barometric Pressure: 29.82 in / 1009.7 hPa (Falling)
  • initial temp.: 24C
  • plate voltage: 502V

Drop 5

  • Up under positive charge on top plate: 1.87, 17.42 (behavior has changed)
  • Down with both plates grounded: 18.23, 15.27, 21.40

Drop 6

  • Up under positive charge on top plate:4.90,4.68, 4.12, 4.42, 5.11
  • Down with both plates grounded: 28.72

Plate Voltage: 506V Temperature of chamber: 25.5c

Drop 7

  • Up under positive charge on top plate: 4.81, 4.65, 5.09, 4.73, 5.06
  • Down with both plates grounded: 48.93, 54.83, 55.55

Switched charge, stopped alpha exposure. Up with opposite charge (negative on top plate): 2.58, 2.21, 4.33, 4.70 Appeared to loose charge.

Drop 8

  • Up under positive charge on top plate: 3.09, 3.09, 3.21
  • Down with both plates grounded: 93.81

Lost it

Chamber temp 26.5 Charge on plates: 507V

Drop 9

  • Up under positive charge on top plate: 10.33, 9.05, 9.17
  • Down with both plates grounded: 10.14, 10.18, 10.05

Exposur begins (under + charge no motion occurs, very stable) lost him

Drop 10

  • Up under positive charge on top plate: 19.02, 18.11, 16.71
  • Down with both plates grounded: 6.09, 5.88, 5.56,

Exposure begins (after a few sec looses charge)

  • Up under positive charge on top plate:
  • Down with both plates grounded: 5.52

lost him

Drop 11

  • Up under positive charge on top plate: 22.67, 5.34 (change in charge noticed), 5.70, 5.36
  • Down with both plates grounded: 5.31, 5.90, 5.93, 5.83

Exposure begins (won't go up, but can increase speed downwards, thus we determine the oil particle must have been too massive to rise under the force of one e-charge)

Chamber temperature: 27.8c Plate voltage: 507V

Drop 12

  • Up under positive charge on top plate: 8.93, 8.84, 4.12, 3.48
  • Down with both plates grounded: 22.00, 22.34, 25.62

Exposure begins (charge is quickly reversed)

  • Up under negative charge on top plate: 3.68, 3.50, 3.65, 3.43, 1.15, 1.15, 1.30, 1.21, 1.36
  • Down with both plates grounded: 22.70, 20.45

chamber temperaturte: 28C

Voltage: 506.5V

Drop 13

  • Up under positive charge on top plate: 2.58, 2.45, 2.98
  • Down with both plates grounded: 17.34,

premature end to data aquisition

Drop 14

  • Up under positive charge on top plate: 1.81, 2.00, 1.58
  • Down with both plates grounded: 7.08, 7.63, 7.75

Exposure begins (no change for a while, then noticable slow down)

  • Up under positive charge on top plate: 15.53, 20.33, 15.95, 17.81, 19.33
  • Down with both plates grounded: 7.46, 7.87

Second Exposure

  • Up under positive charge on top plate: 13.27, 1.15, 1.18, 1.21
  • Down with both plates grounded: 6.59, 7.43

Temperature remains at 28°C.

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