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Homework Help: Faraday's experiment

  1. Mar 22, 2012 #1
    1. The problem statement, all variables and given/known data

    The coils which first produced a slight but detectable kick in Faraday's galvanometer he describes as made of 203 feet of copper wire each, wound around a large block of wood. The turns of the second spiral (that is, single layer coil) were interposed between those of the first, but separated from them by twine. The diameter of the copper wire itself was 1/20 inch. He does not give the dimensions of the wooden block or the number of turns in the coil. In the experiment, one of these coils was connected to a "battery of 100 plates." (Assume, that one plate is roughly 1 volt.) See if you can make a rough estimate of the duration in seconds (it will be small) and magnitude in amperes of the pulse of current that passed through the galvanometer.

    2. Relevant equations

    3. The attempt at a solution

    If someone could verify these:

    V - I1R - LI1' - MI2' = 0 and
    0-I2R - LI2' + MI1' = 0 and M = L

    Some from there I added the two equations and assuming that I1 = V/R(1-e^(-R/L)t) I plugged that in and solved the differential equation for which I got I2 = V/R(2-e^(-R/L)t

    and then I'm at a loss form what to do...
  2. jcsd
  3. Mar 22, 2012 #2


    User Avatar

    Staff: Mentor

    Perhaps you are supposed to look at inductance formulae for air core coils, involving wire diameter, number of turns/inch, and diameter of former?
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