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Homework Help: A Single Turn, Square Loop (torque)

  1. Feb 14, 2010 #1
    1. The problem statement, all variables and given/known data
    A 0.790 m length of wire is formed into a single-turn, square loop in which there is a current of 12.4 A. The loop is placed in a magnetic field of 0.146 T, as shown in the figure below.

    http://img294.imageshack.us/img294/5043/cutj2167.gif [Broken]
    2. Relevant equations

    Net torque = NIABsin(theta)

    3. The attempt at a solution
    Okay so looking at the problem. I see that a wire the length of .790 is bent to for a single-turn square. So I take my length and divide it by 2. Which should be the length of each side of the square now.
    Now the area of a square is A = l*w or one of your sides squared. So that would give me an A of .156 m^2.

    Now as for N should it not just be 1. Since its a single turn square.

    B = .146
    I = 12.4
    Also since im looking for the maximum torque it should be a sin(90) correct?

    Well anyway when I use this formula I'm not getting the correct answer. So if someone could steer me in the right direction that would be great :).
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 15, 2010 #2


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    How many sides does a square have?

  4. Feb 15, 2010 #3
    A square has 4 sides. But since its a single loop square doesn't it only have 2 sides?
  5. Feb 15, 2010 #4
    I mean not that the square in general has 2 sides. I know thats not possible. But I thought that when it said a single turn it meant that the length .709 was the first 2 sides of the square... |_ <- like that if it makes sense. And I just divided the length by 2 to get the length of one side. Anyway thats what I think of when it says single turn.
  6. Feb 15, 2010 #5


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    Well, it might have been better to say "single loop" in the problem. You need the area of the loop to get the torque. A single turn "L" shape has no area.

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