MAKE YOUR OWN DC ELECTRIC MOTORMAKE YOUR OWN DC ELECTRIC MOTORMaterials:

D-cell, disk magnet, rubber band, 2 large paperclips, scissors, sand paper, 2-3 feet thin wire, nail

Procedure:

1. Take the 2-3 foot piece of thin wire and wrap it around the D-cell. The total number of wraps depends on the gauge (“thinkness”) of the wire.

2. “Tie” the ends of the wire through the loops so that the loop of wire will remain in place when you let go. Make sure they are 180°apart along a diameter of the loop. It is veryimportant for the loop to be “balanced.” Tryto spin it freely between your fingers.

3. Bend the paper clips in order to form loops on their ends, which will be used for holding the wire loop. They should look like the ends of safety pins.

4. Secure these to the dry cell with the rubber band. Place the magnet on the dry cell and place the wire loop in itsholders. Observe what happens.

5. Disappointed that nothing happened? The reason is that the wire is insulated with paint, which must be scraped off. This is the trickiest part. Whether or not the ends of the wire loop are scraped correctly will determine the success of your motor.

6. Hold the wire loop vertically between your thumb and Index finger of one hand near the edge of the table (desk) so that the wire end lies on the table.

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7. Use the other hand and the sand paper to scrape the insulation off the top half of the wire. If you scrape too much, use a permanent marker to “repaint” the insulation.

8. Turn the wire loop around and scrape the top half of the wire on the other end.

9. Place the wire loop into its holders and move the loop so that it lies just above the magnet. The motor should now begin spinning. If not, you may need to give it a little push to get it going. A nicely balanced loop and proper scraping are essential to the performance of this motor.

Other instructions and pictures of electric motors madein similar ways may be found on the World Wide Web at:

http://fly.hiwaay.net/~palmer/motor.html http://www.exploratorium.edu/snacks/stripped_down_motor.html

http://www.scitoys.com/scitoys/scitoys/electro/electro.html#motor http://www.evilmadscientist.com/article.php/HomopolarMotor

Extension:

Why is it necessary to scrape only the top half of each wire?

Observe the direction your motor spins. Turn the magnet over and observe again. What do you notice?

Draw a diagram using the rule for force on a current bearing wire or moving charge when in the presence of a magnetic field in order to explain why this motor works.

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