PreLab – Capacitors 2 Name:

Q = C V	E = ∆V / ∆x				where epsilon “naught” (8.854 x 10^-12 F/m) is defined as permittivity of free space OR electric constant OR distributed capacitance of the vacuum
E = k Q / r^2	E = F / q
E = 1/4πε0 Q / r^2	F = k Q q / r^2
Our lab manual demonstrated a classic derivation, please review equations 1 to 5.					Please don’t confuse with mu “naught" (μ0 = 4π x 10^-7 H/m; H/m = N/A^2) · permeability of free space · magnetic constant permeability of vacuum
At the surface of sphere the E = Q / (ε0 4πr^2) E = Q / A ε0 Surface area of sphere is _________ What would your potential equal when at infinity if you had a circular conductor in Electric fields lab (Hint: if the conductor is 10 Volts, the first potential line out would be 9 Volts, your next would be 8 Volts, etc) _________			And the potential on the sphere is related to the electric field by V(∞) – V (R) 0 - ∫ E ∙ dl 0 - ∫ Q / ε0 4πr^2 ∙ dr V = Q / ε0 4πR Where Q = C V C = 4πε0R C = 4πε0R (R/R) C = A ε0 / d (dist “d” is distance from center) Cint-theory = A ε0 / d				3. Why do you hold the GND connection located on the electrometer? a. To keep from being “shocked” b. To protect the capacitors from static buildup c. To eliminate coupling to other nearby charged sources d. All of the above 4. Calculate your theoretical internal capacitance of parallel plate capacitor of dimensions 18 cm diameter with distance between plates of 10 mm
Graph the data from part B Using the slope determined from Part B graph (to the right) and the theoretical value of capacitance from #4; calculate the internal resistance of your electrometer.
Figure 6-3 ln V(t) = -(1/RC) t + ln Vmax y = m x + b		Volt		Time (sec)
		55		15
		50		73
		45		139
		40		211
		35		295