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Homework Help: Magnetic Flux passing through loop

  1. Aug 10, 2009 #1
    1. The problem statement, all variables and given/known data
    The magnetic field in a certain region is given by B=<40i-18k>T. How
    much flux passes through a 5cm^2 area loop in this region if the loop
    lies flat in the xy plane?

    2. Relevant equations

    3. The attempt at a solution

    I got the answer (90 * 10^-4) in negative, and its in positive in the textbook at the back...
    How can flux be negative and why can we drop the negative sign?
  2. jcsd
  3. Aug 10, 2009 #2

    Gib Z

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    Homework Helper

    The amount of flux can be thought of as always a positive quantity, whilst the sign of the value dictates direction based on a previously decided convention. For example, if we define Up to be the positive direction, and we have 5 Wbs of flux downwards, we can express that as -5 Wbs. The sign tells you the direction the flux acts in, the sign tells you the direction.
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