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Homework Help: Electromagnetic Repulsion

  1. Mar 26, 2015 #1
    1. The problem statement, all variables and given/known data
    I have made an electromagnet using the primary core of a microwave oven transformer and a 1.5 D cell battery.

    I would like to use the electromagnet to repel an aluminum bar (1 in. dia., 3 in. in length, and 1/4 in. thick; it is shown in the picture)

    For some reason, the electromagnet only attracts to ferrous metals, but does not repel non ferrous metals (like the aluminum bar). According to my research, some non ferrous metals will not be repelled by electromagnets, but aluminum should definitely be repelled.

    I've attached a picture of my electromagnet

    2. Relevant equations

    3. The attempt at a solution
    I've done everything I can think of to try and make the electromagnet repel the aluminum bar. I've tried switching the wires from positive to negative and vise versa, changing the battery size, and changing the thrust direction.

    What can I do to make my electromagnet repel this aluminum bar?


    Attached Files:

  2. jcsd
  3. Mar 26, 2015 #2


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    Aluminum is paramagnetic, so it has a slight attraction to magnetic fields.
  4. Mar 27, 2015 #3
    But, shouldn't non ferrous metals like aluminum and copper be repelled due to Eddy currents?
  5. Mar 27, 2015 #4

    rude man

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    You don 't get eddy currents with a dc magnetic field.
    As for when you thrust, that force is probably too weak and of too short duration to move the metal.
  6. Mar 27, 2015 #5
    Sorry, I'm kind of new to this. So, if I wanted to create eddy currents, how would I adjust my model to use an ac power source?
  7. Mar 27, 2015 #6

    rude man

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    For safety's sake I suggest a step-down transformer 115V to maybe 26V (a common type), then you need a resistor in series with your coil to keep the current manageable. Idea is not to overload the transformer.
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