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Homework Help: Finding current! problem, where did i mess up?

  1. Nov 25, 2005 #1
    The conducting rod shown in Figure 30-52 has a length L and is being pulled along horizontal, frictionless, conducting rails at a constant velocity v. The rails are connected at one end with a metal strip. A uniform magnetic field B, directed out of the page, fills the region in which the rod moves. Assume that L = 10 cm, v = 7.7 m/s, and B = 1.9 T.
    Here is the picture:

    (a) What is the magnitude and direction of the emf induced in the rod? (Take up to be positive.)
    I got: 1.463 which was correct.

    (b)What is the magnitude and direction of the current in the conducting loop? (Take counterclockwise to be positive.) Assume that the resistance of the rod is 0.40 OHMS and that the resistance of the rails and metal strip is negligibly small.
    I used

    EMF - IR = 0;
    I = EMF/R;
    I = 1.463/.40 = 3.6575 which was wrong, any ideas were i messed up? Thanks.
  2. jcsd
  3. Nov 25, 2005 #2


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    Homework Helper

    The positive charges in the rod, moving to left, are pushed UPWARD
    (by the right-hand-rule, okay?), which is in the CLOCKWISE sense.
    If COUNTER-clockwise is called positive, your current will be negative.
  4. Nov 26, 2005 #3
    Ahh thank you lightgrav!!
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