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Homework Help: Energy stores in RL circuit

  1. Oct 25, 2011 #1
    1. The problem statement, all variables and given/known data

    An inductor initially has 3 A of current passing through it at time t = 0. The current through the inductor increases at a constant rate until 5 A of current is flowing through it 1s later at t = 1 s. The voltage across the inductor is 4 μV while the current is increasing. What is the increase in the energy stored in the inductor between t = 0 and t = 1 s?

    Answer: 16 μJ


    2. Relevant equations

    KVL, KCL

    3. The attempt at a solution

    I can use U=1/2 I^2L to find the energy? But how enery increased? And how can I find current over inductor?

    Thx
     
  2. jcsd
  3. Oct 25, 2011 #2

    gneill

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    Staff: Mentor

    I suggest that you find the inductance L first. What's the defining formula for inductance (hint: it involves a derivative).

    Once you have the inductance you can determine the energy stored for each level of current.
     
  4. Oct 26, 2011 #3
    So I just use V/ (dl/dt)?
     
  5. Oct 26, 2011 #4

    gneill

    User Avatar

    Staff: Mentor

    Try it and find out!
     
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