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Homework Help: Induced EMF in a loop

  1. Dec 6, 2004 #1
    Here is a bonus question that I was given yesterday. I am completely at a loss of what to do. Any suggestions?

    A conducting loop with a half circle of radius r=0.20m and 3 straight sections. The half circle lies in a uniform field B that is directed out of the page. The magnitude of B as a function of time is given by B(t) = 4.0t^2 + 2.0t + 3.0 where B is in Teslas and t is in seconds. An ideal battery with EMF E=2.0V is connected to the loop. The loop has a resistance of 2.0 Ohms.
    a) Find the magnitude and direction of the EMF induced in the loop.

    b) What is the current in the loop at t = 10 seconds?
  2. jcsd
  3. Dec 6, 2004 #2
    just use the equation for induced emf: -dflux/dt.
    flux = B(t)*area of half circle
    add this emf as a function of time to the battery emf of 2.0V. I think you add, at least. they tell you the B field is directed out of the page, but they don't tell you which way the battery is connected... anyway, add 2 + (-dflux/dt) and this is your emf in the loop as a function of time. then use v = ir to calculate i(t).
    Last edited: Dec 6, 2004
  4. Dec 6, 2004 #3
    But how do I find the direction of the EMF?
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