1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Induced emf at a specific time

  1. Oct 28, 2009 #1
    1. The problem statement, all variables and given/known data


    A circular coil with 35 turns of wire and a diameter of 19 cm is placed in a magnetic field given by B(t) = 6 t^2 + 6 t + 2 T where t is time in seconds. The field is perpendicular to the plane of the coil. What is the induced EMF at t = 5 s?

    2. Relevant equations


    E=-d(magnetic flux)/dtime

    3. The attempt at a solution
    I found E to be 36.12 V but that's wrong. I'm not sure what's wrong. I did E=NAB/time.
     
    Last edited: Oct 28, 2009
  2. jcsd
  3. Oct 28, 2009 #2
    Emf is proportional to negative the derivative or rate of change of the magnetic flux with respect to time. The area is constant, thus
    V = -NA*dB/dt.
     
  4. Oct 28, 2009 #3
    I plugged in -36.12 but it's still wrong. Can we have a negative voltage?
     
  5. Oct 28, 2009 #4
    Could you please tell me where I'm wrong? I have a couple of hours left.
     
  6. Oct 28, 2009 #5
    dB/dt = 12t + 6; at t = 5s, dB/dt = 66T/s
    N = 35 turns
    A = pi*r^2...so your problem might be that you're using the diameter of 19cm instead of the radius; also, be sure that you convert the given units to the proper units, so the radius = d/2 = 9.5cm = .095m.
    The emf is V = -NA*dB/dt....and you could have a negative voltage.
     
  7. Oct 28, 2009 #6
    Thank you very much I appreciate it.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Induced emf at a specific time
  1. Induced EMF (Replies: 1)

  2. Induced EMF (Replies: 4)

Loading...