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Homework Help: Field strength and energy of electrons in a magnetron

  1. Feb 25, 2008 #1
    1. The problem statement, all variables and given/known data

    The microwaves in a microwave oven are produced in a special tube called a magnetron. The electrons orbit the magnetic field at 2.4 GHz, and as they do so they emit 2.4 GHz electromagnetic waves.

    a) what is the magnetic field strength?
    b) if the maximum diameter of the electron orbit before the electron hits the wall of the tube is 2.5 cm, what is the maximum electron kinetic energy?

    2. Relevant equations

    frequency = qB/2(pi)m

    3. The attempt at a solution

    2.4 GHz = (1.6 x 10^-19)(B)/ 2(pi)(9.109 x 10-31)

    then solve for B. is that right?

    I dont understand part (b) at all
  2. jcsd
  3. Feb 25, 2008 #2


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    Gold Member

    Well, yes, the first part is just plugging in numbers and calculating.

    The second part requires you to calculate the tangential velocity of an electron moving in a circle of diameter 2.5 cm with an angular velocity omega = 2*Pi*2.4 GHz. Given that you can work out the KE.
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