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EMF, Induction Help!

  1. Jul 26, 2009 #1
    1. The problem statement, all variables and given/known data
    1. A 109.3 mH inductor whose windings have a resistance of 3.6 Ω is connected across a 11 V battery having an internal resistance of 1.83 Ω. How much energy is stored in the inductor?

    2. The maximum allowable potential difference across a 225.7 mH inductor is 401 V. You need to raise the current through the inductor from 1.28 A to 3.88 A. What is the minimum time you should allow for changing the current?


    2. Relevant equations
    EMF(max)=wNBA
    w=angular momentum
    N=number of loops
    B=magnetic field
    A=area


    3. The attempt at a solution

    For both of these what seem to be similar problem I am hitting a dead end!
     
  2. jcsd
  3. Jul 26, 2009 #2

    diazona

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    I thought of something entirely different upon seeing wNBA...

    Anyway, here's a hint: #1 asks for the energy stored in an inductor. Do you know a formula for that?

    For #2, do you know an equation for the voltage (potential difference) across an inductor?
     
  4. Jul 27, 2009 #3
    #1 U=.5L*I^2


    #2
    V=-L(dI/dt)

    d I= delta flux
     
  5. Jul 27, 2009 #4

    diazona

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    Yep, that's right. Note that in both cases, I is electrical current (I hope you knew that).

    Now do you have any ideas about how to use those formulas?
     
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