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Homework Help: Charged Particles Moving in Magnetic Field

  1. Mar 31, 2008 #1
    The picture tube in a television uses magnetic deflection coils rather than electric deflection plates. Suppose an electron beam is accelerated through a 50.0 kV potential difference and then through a region of uniform magnetic field 1.00 cm wide. The screen is located 10.0 cm from the center of coils and is 50.0 cm wide. When the field is turned off, the electron beam hits the center of the screen. What field magnitude is necessary to deflect the beam to the side of the screen? Ignore relativistic corrections.

    I'm thinking the coil extends to the screen...so it would be a coil being around 20 cm long and 1 cm wide. I can find the entrance velocity of the electron beam using the given voltage...after that point I'm stuck. Assuming the magnetic field is perpendicular to the velocity, the magnetic force should produce a centripetal motion that lasts only up until the particle moves 0.5 cm to the side from the central axis of the coil. From that point, the tangential velocity, which would have a magnitude equal to the one calculated using the voltage, would carry the particle to the side of the screen. I'm not sure of how to continue on from there.
  2. jcsd
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