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Homework Help: Magnetic fields/ force on conductors

  1. Sep 1, 2008 #1
    1. The problem statement, all variables and given/known data
    calculate a value for B at a distance of 50cm, in ,air, from a long straight cable carrying a current of 1000A.

    2. Relevant equations
    I=q\t = qv/l

    3. The attempt at a solution
    i have not been able to calculate an answer as there are constantly two unknowns and i am unable o fine F.
  2. jcsd
  3. Sep 1, 2008 #2
    i believe the answer is 4 x 10 to the -4 telsa
  4. Sep 1, 2008 #3
    You're being asked to find magnetic field and not force due to the magnetic field, right?

    The equations you wrote allow you to find the force due to a magnetic field, once you already know what B is. However, right now you're trying to find B due to the current. You need a different equation, that's hopefully in your book that relates B and current I.
  5. Sep 1, 2008 #4


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    Homework Helper

    yeah johnj7 is right. You need the proper equation. Look in your textbook for an equation relating B to a current carrying wire. Check online as well. If you're desperate and have learnt what is known as the Biot-Savart law, you can derive B from there.
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