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Homework Help: Torque, magnetic field

  1. Nov 17, 2008 #1
    1. The problem statement, all variables and given/known data
    The rotor in a certain electric motor is a flat, rectangular coil with 80 turns of wire and dimensions 2.50 cm by 4.00 cm. The rotor rotates in a uniform magnetic field of 0.800 T. When the plane of the rotor is perpendicular to the direction of the magnetic field, it carries a current of 7.5 mA. In this orientation, the magnetic moment of the rotor is directed opposite the magnetic field. The rotor then turns through one-half revolution. This process is repeated to cause the rotor to turn steadily at 3600 rev/min.

    (a) Find the maximum torque acting on the rotor.
    (b) Find the peak power output of the motor.
    (c) Determine the amount of work performed by the magnetic field on the rotor in every full revolution.
    (d) What is the average power of the motor?

    3. The attempt at a solution

    I have solved part A) and found the max torque to be 4.80 e(-4) Nm. I am stuck on part b. I can find the max and min potential energy of the system but I don't know how that would help. Not sure how to go about this part.
  2. jcsd
  3. Nov 18, 2008 #2
    Last try, can anyone help me get part b?
  4. Nov 18, 2008 #3


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  5. Nov 18, 2008 #4
    Thanks for the link, but I am still confused on this problem.

    I have the max torque so I though I could calculate the max power since P = tw and I have the angular velocity. But that didn't work. If anyone has an ideas I would be grateful.
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