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Simple Motor

AUG 01, 2017
Member Contributor

This experiment will show students how to build a simple electric motor. This is best for students twelve and older as it requires some delicate work.

  • Figure 2 - Slide the wire off the pen to create a coil. Diameter is ~1 cm.

    Figure 2 - Slide the wire off the pen to create a coil. Diameter is ~1 cm.

    Figure 3 - The fully assembled electric motor. Photos courtesy of Jacob Robertson and Zakary Noel, 2017 SPS SOCK interns.

    Figure 3 - The fully assembled electric motor. Photos courtesy of Jacob Robertson and Zakary Noel, 2017 SPS SOCK interns.

    An electrical current through any conductor creates a magnetic field. This was discovered (some say by accident) by Hans Christian Oersted in 1820 when he noticed a nearby compass needle was deflected when he turned on his electrical equipment. You can see the same effect with your coil circuit and a compass.1,2

    Wrapping the wire into a coil increases the strength of the magnetic field, so long as the moment of inertia remains small.

    The principles that allow this motor to work are the same ones that govern all motors. These motors all turn electromagnetic energy into kinetic energy. Generators work the opposite way, by turning kinetic energy into electromagnetic energy (and in fact, you can turn motors into generators and vice versa, although sometimes it takes a little work).

    Why isn’t it working?
    This relatively simple motor can take some patience. The answer to this most common question could be a number of issues. Try some troubleshooting:

    Make sure your safety pins have good contact with the battery terminals.

    • Make sure you didn’t sand off too much of the wire insulation—one end needs to have enough insulation on one side that the circuit is broken as the coil spins.
    • If the coil is leaning too far to one side, you may need to rewrap it so it’s more symmetrical.
    • Try spinning the coil the other direction.

    Instructions for building an even simpler motor using a battery, a magnet, wire, and a drywall screw can be found here. Watch out with this one, and use eye protection as the screw could go flying.
    http://www.evilmadscientist.com/2006/how-to-make-the-simplest-electric-motor/

    Instructions for building a more advanced motor that doesn’t require a push to get started can be found in The Physics Teacher, the journal from AAPT, “Development of a New Method for Assembling a Bipolar DC Motor as a Teaching Material.”
    https://aapt.scitation.org/doi/10.1119/1.4981037

    References

    1. R. P. Feynman, R. B. Leighton, and L. L. Sands, The Feynman Lectures, vol. 1 (Addison-Wesley, 1963-1965), chapter 16.
    2. R. D. Knight, B. Jones, and S. Field, College Physics, 3rd ed. (Pearson, San Francisco, CA, 2014).

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