Electrostatic Experiment: Charge, Potential and Capacitance Experiment number: 2 Date: 1/29/2008
Purpose: The purpose of this lab is to become accustomed to electric charge, electric potential, and capacitance. It also gives knowledge to how mechanical work and electrical potential are connected. Apparatus: Items needed for this experiment are: 1. A rubber rod 2. A wool cloth 3. A glass rod 4. A silk cloth 5. String 6. Pith Ball 7. Lab Stand 8. Electrometer 9. Ceramic Spacer 10. Parallel Plate Capacitor 11. Ruler 12. Vernier Caliper. Method: In part one we used the wool cloth and rubber rod to create a charge on the ball. Then, we used the silk cloth and glass rod to illustrate that the ball had a charge by showing that it was attracted to the glass rod. For the rest of the experiment the rods and cloths were used with the plates and the electrometer to collect the remaining data. Results: The rubber rod and wool cloth created a negative charge on anything it touched such as the ball and also the plates. This was shown by the electrometer. In the same way, the glass rod and the silk cloth created a positive charge on anything it touched. This was also shown by the electrometer. The ball also confirmed that the glass rod had a positive charge because, after it had been negatively charged by the rubber rod, the ball was attracted to the glass rod. Interference: The results were no different than what I expected. Conclusion: In conclusion, lab this allowed us to visualize electric charge, electric potential, and capacitance. It showed how something charged could touch the plates and transfer the charge from the initial object to the plates.
DATA ORGANIZATION SHEET DETERMINE CAPACITANCE OF THE ELECTROMETER AND CABLE, CE Area of each plate A = __0.04715__ (m2) d = thickness of spacers = __0.006__ (m)
Distance between plates CP =
0A
/ d = 6.9546 x 10-11_ (F)
DATA Trial No. 1. 2. 3. 4. Vi -90 -100 -100 -85 Vf -30 -55 -70 -75
CALCULATIONS Vf / (Vi Vf) 0.5 1.22 2.33 7.5
Average Vf / (Vi Vf) = ___2.88____ CE = CP Vf / (Vi Vf) = __2 x 10-10 (F)
DETERMINE CAPACITANCE OF PLATE WITH 4 SPACERS, CP' DATA Trial No. 1. 2. 3. 4. 5. Vi -95 -85 -80 -80 -90 Vf -50 -70 -75 -75 -50 CALCULATIONS (Vi Vf) / Vf 0.9 0.21 0.07 0.07 0.8
Average (Vi Vf) / Vf = ____0.41____ CP' = CE (Vi Vf) / Vf = __8.2 x 10-11_ (F) Calculated value of CP =
0A
/ d' = 4.17 x 10-11_ (F) (when d' is thickness of 4 spacers)
' CP CP x 100% = __96.64__ % CP
Comparison of calculated and measured values
DETERMINE CAPACITANCE WITH GLASS DIELECTRIC AND FIND THE DIELECTRIC CONSTANT
Thickness of rubber plate
d' = __0.012___ (m)
DATA Trial No. 1. 2. 3. 4. Vi -85 -80 -80 -80 Vf -25 -15 -15 -15
CALCULATIONS (Vi Vf) / Vf 2.4 4.33 4.33 4.33
Average (Vi Vf) / Vf = ____3.85____ Cd' = CE (Vi Vf) / Vf = __7.7 x 10-10_ (F) Cair =
0A
/ d' = ___4.17 x 10-11___ (F) k = Cd' / Cair = __18.47__
Dielectric Constant