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Homework Help: (101) Broadcast circut

  1. Apr 20, 2008 #1
    1. The problem statement, all variables and given/known data
    Consider the broadcasting circuit for an AM radio station which broadcasts at a frequency of 550 kHz. The electrons in such a circuit are moving back and forth in simple harmonic motion.

    (a) How long does it take for the free electrons in this circuit to go back and forth once? Give your answer in μs.

    (b) Assuming the average speed of the electrons is 100 μm/s, what is the range of motion of the electrons as they go back and forth in the wires of the circuit. (HINT: As the electron goes back and forth, it travels its full range every half cycle.) Give your answer in nm.

    2. Relevant equations

    3. The attempt at a solution

    the answer to a was easy - just the reciprocal of 550khz.

    b, seems a little more confusing. I know the speed (100x10^-6) of the electrons, and the time (answer a), but my confusion is in the "hint". Would I multiply the time by 2?

    Thank you!
  2. jcsd
  3. Apr 20, 2008 #2


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    Homework Helper
    Gold Member

    The hint is telling you that the electrons are traveling the full range of motion in 1/2 of a period.
  4. Apr 20, 2008 #3
    Ok, so I multiplied v(100x10^-6) by (1/2)(1.818x10^-6) and got 9.09x10^-11. It asks for the answer in nm (^-9), so I entered 90.9, and it was incorrect. Can someone tell me what I am doing wrong? I only have 1 attempt left.
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