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    http://www.youtube.com/watch?v=4LHaTXQawSM

    need help to explain the effect!!
    There is d.c. current passing through the coil.
    And the coil starts moving in a SHM form.
    However, I dont think it is a SHM as the acceleration varies.
    Explanation plz !!!

    It's a part of my coursework and the video is taken by myself.
    Voltage: 15.3V
    Initial current: 6.7A
    It's an iron rod inside the coil.
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    (Original post by sirhcyin1)
    http://www.youtube.com/watch?v=4LHaTXQawSM

    need help to explain the effect!!
    There is d.c. current passing through the coil.
    And the coil starts moving in a SHM form.
    However, I dont think it is a SHM as the acceleration varies.
    Explanation plz !!!

    It's a part of my coursework and the video is taken by myself.
    Voltage: 15.3V
    Initial current: 6.7A
    It's an iron rod inside the coil.
    What do you think the explanation might be?
    As it's your coursework you need to think about this first before asking others to provide an explanation.
    As a start think about
    *the magnetic field generated in the coil when a current flows in it
    *the magnetic field induced in iron
    *the attraction and repulsion of N and S poles
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    Those theories behind the experiment are already included in my write-up. However, the problem is that, I am not sure why the amplitude of oscillation varies with the time. Is it because of the change of magnetic force induced along the rod or other factors? What are the other factors?
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    (Original post by sirhcyin1)
    Those theories behind the experiment are already included in my write-up. However, the problem is that, I am not sure why the amplitude of oscillation varies with the time. Is it because of the change of magnetic force induced along the rod or other factors? What are the other factors?
    Have you studied electromagnetic induction. In particular Lenz's Law?
    Moving coils and magnets generate emfs. (Faraday's Law.)
    Take a look at (or search for) "eddy currents" and this will lead you to the explanation.
    Here's a start
    http://en.wikipedia.org/wiki/Eddy_current_brake
 
 
 
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