University of California, San Diego
Physics 1b - Thermal Physics & Electromagnetism

H. E. Smith   Spring 2000

Physics 1B - Tutorial #6

  1. In the network above, each capacitor has a capacitance of 2µF.

  2. A capacitor made of a close pair of conducting plates, as shown above, is charged then discharged to produce a spark. The plates are charged a second time, and this time the plates are pulled further apart before being discharged. Will the second charge be (a) bigger than, (b) the same as, or (c) smaller than the first spark. Explain your reasoning.

    The charge remains the same, but you are doing work pulling the plates apart, increasing the potential energy stored in the capacitor, PE = Q2/2C, where C = A/l has decreased becaused "l" has increased. Same charge, greater energy --> "bigger" spark.

  3. A mountain lake is to be used as the water supply for an alpine village which lies a vertical distance h below the lake. The lake and village are to be connected by a system of pipes. How will the flow of water depend upon:

    What would happen if you put in two parallel pipes of the same length & diameter?
    You would double the flow.

    What would happen if you doubled the length of the pipe?
    You would decrease the flow.

    What does this have to do with electricity?

  4. Above is a diagram of the electrical system of an automobile. Which swithces (A, B, C, D, E, F) must be closed in order to Note that the whole body of the car, including the engine is wired together as a common ground. (Hecht: Ch. 19 #23, p. 749)

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Gene Smith

Last modified: Tues., 16 May 2000