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Homework Help: Faraday's Law of Induction and EMF

  1. May 24, 2007 #1
    1. The problem statement, all variables and given/known data

    A coil of 15 turns and radius 10cm surrounds a long solenoid of radius 2cm and 1x10^3 turns/m. The current in the solenoid changes as I = (5A)sin(120t). Find the induced emf in the 15-turn coil as a function of time.

    2. Relevant equations

    emf = -Nd[flux]/dt

    d[flux] = int[B*dA]

    3. The attempt at a solution

    I have no idea how to start this. I tried doing some basic problems, but I just do not understand any of it.
  2. jcsd
  3. May 24, 2007 #2

    Doc Al

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    Staff: Mentor

    What's the magnetic field inside a solenoid? What magnetic flux passes through the coil?
  4. Oct 30, 2008 #3
    Never mind, I posted my own thread.
    Last edited: Oct 30, 2008
  5. Oct 30, 2008 #4


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    Staff Emeritus
    Science Advisor
    Gold Member

    What is the difference between a coil and a solenoid? (I'm asking the question seriously).
  6. Oct 30, 2008 #5
    For this problem:



    In general people may (and will) say "coil" for the second case too.
  7. Nov 1, 2008 #6
    Did you consider using the mutual inductance of the coil-solenoid system?

    I have a theory question for you that might help to get you started on this problem:

    What special characteristic of Mutual inductance helps us to quickly and easily solve problems like this?

    Good luck,

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