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Homework Help: Force in a magnetic field. Need help using the equation

  1. Sep 28, 2008 #1


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    1. The problem statement, all variables and given/known data

    What is the magnitude of the force per meter of length on a straight wire carrying a 6.70-A current when perpendicular to a 0.89-T uniform magnetic field?

    What if the angle between the wire and field is 45.0°?

    I know how to do the whole thing, I just can't get my answer right. I don't know if I am working the equation out right.

    2. Relevant equations


    3. The attempt at a solution

    Using the above equation. For part A I know that I use it for 90 degrees at 1m


    Part B is the one I can't get the answer to.


    **I haven't had a trig class or a physics class for about 7 years so I don't remember how to exactly use sin. For Part A I got the correct answer because I just didn't use the sin. I just took the (6.70A*0.89T). Can someone explain how to use sin or how to get the right answer. I got 5.07 N/m but that is not correct.

    Thanks in advance to everyone that helps.
  2. jcsd
  3. Sep 28, 2008 #2


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    Homework Helper
    Gold Member

    It sounds like you had your calculator set to radians instead of degrees.

    1 degree = pi/180 radians so 45 degrees= 45pi/180 =pi/4 radians

    Try using that as your argument for sin.
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