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Electric Energy Potential and Capacitors

  1. Oct 2, 2011 #1
    1. The problem statement, all variables and given/known dataSo this is from a past test put up as a study guide, but I'm stumped here. The question is:

    A spark jumps between two electrodes, transferring a charge of 5 μC in 2 × 10−3 s. The
    constant current I that would transfer the same charge in the same time is

    3. The attempt at a solution
    The solution is 2.5e-3A.

    What is the formula to use? Is this to be treated as a capacitor therefore U=1/2QC? Just need a nudge to get my head around it for the test Tuesday.

    Thanks
     
  2. jcsd
  3. Oct 2, 2011 #2

    PeterO

    User Avatar
    Homework Helper

    It is not a formula you need, it is contemplation of units.

    Current is usually quoted in amperes, which means 1 Coulomb per second.
    this spark involved much less that 1 Coulomb, but transferred in much less than a whole second. Think about it.

    [Or use I = Q/t if you must]
     
  4. Oct 2, 2011 #3
    Thanks. I can never remember the various SI units for things. I end up sticking to Amp, Volt, etc, and this seems to be the down fall of my understanding. But they just don't stick. Anyway, I know the time was fast, and would play a key part, but not where.

    Cheers
     
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