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Cary M. Dougherty 18:24, 17 September 2007 (EDT)


our goal is to correctly measure thevelocity of an oil drop in between two capacitors with them just falling and then controlling them with a current. we want to correctly measure the charge, radius, and the mass with only velocities and constants of pressure, density, viscosity, and acceleration.


starting this experiment was disasterous the first time. we set up the experiment exactly as it was told in the manuel. yet the first day we couldn't see any oil falling into the seperation between the capacitors. the second day was a complete success. we adjusted the vertical and horizontal components of the light and also the focus on the wire as i mentioned in my ealier weeks lab report. this i think was the key difference to our results. we had the light reflecting off the wire much more bright and the focus was better. with this new setup, we were able to clearly see oil drip into the spacing and were able to view specks of oil moving down the spacer and back up with the voltage moving through the capacitors.


pgs: 7-12

after we were able to view oil in the spacer, we were able to ionize the oil by a switch on the base of the experiment. by ionizing the oil, we allowed the oil to gain excess electrons and become negatively charged.(as i saw on linh's page, we also saw positively charged droplets which means some were positively charged and some were negatively charged) after we picked out a single drop, we were able to measure the time it took to fall between two major spaces (.5mm). we found ones that fell between about12 and 18 sec give or take a few sec. then sending the voltage through the capacitors, we measured the rise time of the same drop of the same distance, but at a much faster veloctity (between 1 and 6 sec.) after a few measurements, we ionized the same drop for a few sec and did the same calculations.


q- the charge of the electron


d-distance between capacitors-8.11mm, 8.10mm, 8.09mm, 8.105mm, 8.095mm <av.> 8.099mm

g- acceleration due to gravity- 9.80665 m/s^2

b- constant 8.20E^-3Pa*m

a- radius in drop measured in meters

R-density of the oil which is 886 kg/m^3

η- viscostity of air

V- potential difference across the plates in Volts

vr- rise velocity

vf- falling velocity

E electric field (found by \frac{V}{d})


14.87 4.81
17.53 4.87
17.17 4.85
18.67 4.57
17.89 4.53
17.77 4.37
15.93 4.56
16.49 4.90
18.97 4.61
18.41 5.11
19.24 2.50

Average Fall time Average Rise time

17.54 s 4.51 s

starting at a voltage of 501.0 V and 2.07 Mega Ohms and ending at a voltage of 501.8 V and 2.041 Mega Ohms (Temp - 24 C, n - 1.842 (Nsm^-2)E^-5)


16.13 2.23
14.29 2.14
14.85 2.47
15.96 1.93
16.49 1.99
14.79 2.25

Average Fall time Average Rise time

15.418 s 2.602 s

with a voltage of 501.4 V and a resistance of 1.945 Mega Ohms (Temp - 26 C, n - 1.8520 Nsm^-2E-5)

then we ionized the drop and took more calculations:

Fall Time (s) Rise Time (s)
12.10 2.10
12.11 1.77
11.75 2.47
12.49 2.67
13.66 4.12
13.10 7.13
Average Fall time Average Rise time
12.535 s 3.376 s

with a voltage of 501.5 V and a resistance of 1.937 Mega ohms (Temp. - 26.5 C, n - 1.8560 Nsm^-2E^-5)


Fall time (s) Rise Time (s)
18.38 3.31
14.38 3.15
14.11 5.14
13.70 5.70
13.8 5.19
14.72 5.52
14.50 5.23
13.13 5.27
15.37 5.37
Average fall time Average rise time
14.67 4.877

with voltage at 501 V and resistance at 1.9982 Mohms (Temp. - 25 C, n - 1.8470 Nsm^-2E^-5)

then we ionized the drop and took more calculations:

Fall time (s) Risa time (s)
13.86 2.19
14.58 2.21
13.09 2.70
14.38 2.46
13.94 2.24
Average Fall Time Average Rise time
13.855 s 2.36 s

at a voltage of 501.9 V and a resistance of 1.976 Mohms (Temp. - 25.5 C, n - 1.8500 Nsm^-2E^-5)


Fall time (s) Rise time (s)
15.97 2.99
14.50 3.13
13.80 2.95
15.50 2.69
15.17 2.75
15.36 3.36
Average Fall time Average Rise time
15.05 s 2.97 s

with a voltage of 500 V and a resistance of 1.923 Mohms (Temp. - 26.5 C, n - 1.8560 Nsm^-2E^-5)

then we ionized the drop and took more calculations:

however as Linh pointed out the speed the drop was traveling made it too difficult for us to synchronize the stop watch with observations. so we only took to more calculations:

Fall Time (s) Rise Time (s)
9.70 0.72
10.32 0.73


pg. 13


SET 1:

vf - 2.85E^-5 m/s

vr - 1.109E^-4 m/s

SET 2:


vf - 3.243E^-5 m/s

vr - 1.922E^-4 m/s


vf - 3.989E^-5 m/s

vr - 1.481E^-4 m/s

SET 3:


vf - 3.408E^-5 m/s

vr - 1.025E^-4 m/s


vf - 3.609E^-5 m/s

vr - 2.119E^-4 m/s

SET 4:

vf - 3.322E^-5 m/s

vr - 1.684E^-4 m/s

SET 1:

radius a= 2.36679E^-10 m

mass m= 4.9204E^-26 kg

charge q= 1.1427E^-24 C

SET 2:


radius a= 2.371E^-10 m

mass m= 4.9453E^-26 kg

charge q= 1.6278E^-24 C


radius a= 2.3781E^-10 m

masss m= 4.9914E^-26 kg

charge q= 1.1621E^-26 C

SET 3:


radius a= 3.3723E^-10 m

mass m= 4.9547E^-26 kg

charge q= 9.4437E^-25 C


radius a= 2.3743E^-10 m

mass m= 4.9673E^-26 kg

charge q= 1.6204E^-24 C

SET 4:

radius a= 2.3716E^-10 m

mass m= 4.9505E^-26 kg

charge q= 1.4318E^-24 C


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