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Homework Help: Magnetic fields

  1. Nov 25, 2006 #1
    an electron moves within a uniform magnetic field of .2T at a speed of 5x10^5 m/s. What is the magnetic force on the electron?

    I used Fm=qvBSin and got 1.6x10^-14N but the answer is that it cant be determined with this info why not?
  2. jcsd
  3. Nov 25, 2006 #2


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    Because you don't know the angle between the velocity of the electron and the magnetic field! You are right that the magnitude of the magnetic field is [itex] F_m = |q| v B sin \theta [/itex] but without the angle [itex] \theta [/itex] you can't find the answer. (how did {\em you} get an answer? I bet that you used an angle equal to 90 degrees!)

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