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Homework Help: Finding time constant of current decay in closed circuit

  1. Sep 3, 2008 #1
    Hi this is my first post so please be nice :)

    1. The problem statement, all variables and given/known data
    The problem has been set up that a circuit containing a resistor and switch is being driven by a power source of unkown potential. The switch is flick to short the power source leaving only the resistor in a closed loop.
    Calculate the current decay.
    Initial current = 100A
    Resistance = 1n[tex]\Omega[/tex]

    2. Relevant equations

    Power = I2R

    3. The attempt at a solution

    I'm not too sure. The power generated, and hence the heat loss can be found to be 1e-5W so thats 1e-5 Joules per second of heat loss.

    I'm not sure if we have enough information. Current decay involving inductance or capacitance is well known but just a resistor in a circuit of 'ideal' conductors?

    I'm assuming it is an exponential decay of form I=I0e-t/[tex]\tau[/tex] but finding the decay constant is proving tricky. Any advice????

    Thanks in advance.
  2. jcsd
  3. Sep 3, 2008 #2
    Sorry, posted in wrong forum. Please delete.
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