HW _8 P213 F09

# HW _8 P213 F09 - about the gravitational force Just before...

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Physics 2213 Homework #8 Fall 2009 Due : the last recitation class of the week of October 26-30. Read: Chapter 24 and Chapter 26. Exercises and Problems (to be handed in) : (1) #24.38 [Dielectric] (2) #24.49 [Gauss’s Law and Dielectric] (3) #24.59 [Capacitor Network] (4) #24.60 [Throw the Switch] (5) #26.39 [Discharging Capacitor] (6) #26.79 [Wheatstone Bridge] (7) #26.87 [Energy and capacitor] (8) Here is an exercise that demonstrates energy is stored in the electric field . Consider 2 parallel plates each with area A. One is positively charged with total charge Q and the other is negatively charged with total charge –Q. Both charges are distributed uniformly. They are suspended vertically, the +Q plate is fixed while the –Q plate is free to move horizontally but must remain parallel. Both plates have a uniform mass density of M/A. Initially they are at rest, separated by a small distance d. What is the force on the –Q plate due to the +Q plate ? (Forget

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Unformatted text preview: about the gravitational force.) Just before they collide, what is the total kinetic energy ? Where does this energy come from ? Is the energy conserved in this case ? Show your work. (9) [Charging Capacitor] The capacitor is initially uncharged, and the switch is open. Then at time t = 0, the switch is closed. a b c d ! + R C S 2 V bc (t) t V cd (t) t V db (t) t (a) Draw graphs showing how each of the labeled voltages below varies with time t, including t < 0 (before the switch is closed) as well as t > 0. For the following questions: ε = 10 V, R = 2000 Ω , C = 400 μF (μF = 10-6 F) (b) What is the current in the resistor just after the switch is closed? Please show your work. (c) What is the final charge on the capacitor after a long time? Please show your work. (d) At what time t is the voltage across the resistor equal in magnitude to the voltage across the capacitor? Please show your work. Switch closed...
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## This note was uploaded on 12/25/2009 for the course PHYS 213 at Cornell.

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HW _8 P213 F09 - about the gravitational force Just before...

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