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Homework Help: Finding period of revolution of an electron (fairly )?

  1. Mar 19, 2012 #1
    Finding period of revolution of an electron (fairly urgent)?

    1. The problem statement, all variables and given/known data

    A doubly ionized atom (charge = +2e) whose mass is 3.65E-26 kg is accelerated by a voltage of 3950.0 V and enters a region where a uniform magnetic field B = 0.0500 T acts perpendicular to its motion.

    a) What is the radius of curvature of the path of the ion in the B-field?

    b) What is its period of revolution?

    2. Relevant equations


    3. The attempt at a solution

    I did the first part, the correct answer is 0.601 m.

    I've tried a few different methods for b), I won't list them all.

    I rearranged the third equation for v, plugged it into the first equation, plugged that into the second equation and rearranged for T.


    Solved that for 0.0000143156 s

    No idea if this is right or not, but I doubt it because I think I need to use voltages and energies, but that didn't work when I tried it.
  2. jcsd
  3. Mar 19, 2012 #2


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    Staff: Mentor

    Re: Finding period of revolution of an electron (fairly urgent)?

    Your result looks okay for T, but you should use scientific notation to avoid all those leading zeros! Also trim for reasonable significant figures :smile:

    If you already had the radius of the circle and speed, you could simply have found the time to travel one circumference :wink:
  4. Mar 19, 2012 #3
    Re: Finding period of revolution of an electron (fairly urgent)?

    Yea, I tried that, but kept getting the wrong answer =/ I think the value I listed was right after all, thanks!
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