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Homework Help: Rate of current changing through an inductor

  1. Jul 14, 2007 #1
    1. The problem statement, all variables and given/known data
    At time t=0 a 45V potential difference is applied to the leads of a coil with inductance L=50 mH and resistance R=180 ohm. At what rate is the current through the coil increasing at t=1.2ms?

    2. Relevant equations

    1) L=EMF/ (di/dt)
    2) L=N(flux)/i
    3)emf=iR

    3. The attempt at a solution

    I thougt you could first find the current at t=o using EMF=iR= .25 A, then you could find the current at t=1.2 ms, by first finding the flux at this time to do this:

    I thought -d(flux)/dt=EMF= 45V. Is it correct to say that the magnetic flux is changing at a rate of 45 wb/s ? and then multiply by time and use equation 2 , however we dont know the number of turns, which is where im stuck

    any hints would be appreciated
     
  2. jcsd
  3. Jul 14, 2007 #2

    Astronuc

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    Staff Emeritus
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