Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

  1. Sep 28, 2008 #1

    crh

    User Avatar

    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

    F=IlBsin[tex]\theta[/tex]

    3. The attempt at a solution

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

    F=(6.70A)(0.89T)sin90=5.9N/m

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

    F=(6.07A)(0.89T)sin45

    **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

    gabbagabbahey

    User Avatar
    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.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook