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Magnetic flux/induced current

  1. Nov 29, 2015 #1
    Hi everyone. I'm a new poster here, so hopefully this is in the right sub forum:

    I'm just interested in seeing if I've got the right idea with my differentiation of magnetic flux in order to find the induced current in a ring of wire, which has it's normal at, say 30° to a magnetic field (which is uniform but has magnitude changing with time). Lets say the area of the wire is A = π r^2 and the magnetic field strength changes with time according to B = c t^2, where c is a constant and t = time.

    Magnetic flux:

    Φ=AB cos 30°

    Φ= (π r^2) (c t^2) cos 30°

    Is it right to say I don't need to differentiate the cos 30, as that is just a constant? Infact, everything is a constant except t^2, therefore the rate of change of the flux is:

    dΦ/dt = (π r^2) (c 2t) cos 30°

    From here, I'm using Ohm's law, and dividing the above by the resistance of the wire, and I've got my induced current. Does that look right? Thanks!
  2. jcsd
  3. Nov 29, 2015 #2


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    That looks right, but should better be posted in the homework forum, because it looks like a typical homework problem about Faraday's Law of Induction.
  4. Nov 29, 2015 #3
    Thanks for the reply. I thought about posting in the homework forum, though it isnt actually a homework question, I just made up the values to see if I had the idea right. But it does follow the same pattern as many questions. Not sure how to delete or move the thread?
  5. Nov 29, 2015 #4


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    No problem. Just keep in mind to post such questions in the homework forum, using the template there, and welcome to Physics Forums!
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