Introduction: Simple Homopolar Motor

Picture of Simple Homopolar MotorPicture of Simple Homopolar Motor

The first homopolar motor was demonstrated by Michael Faraday in 1821. He was experimenting with magnetism and electricity when he discovered the first circular force then known in nature.

This simple motor is a great beginner project for young makers!

Step 1: Materials

Picture of MaterialsPicture of Materials

Materials needed:

  • A few neodymium Magnets
  • AA battery cell (or use a C or D cell)
  • Bare copper wire, around 30 cm (12 inches) long

Step 2: Add a Dimple to the Battery

Picture of Add a Dimple to the Battery

Begin by taking the AA battery and make a small dimple in the cap on the positive end.

To make the dimple, use a small nail, screw driver or even a multi-tool.

Be careful not to strike the battery too hard, just hit it with enough force to leave a small dimple visible in the cap. Don’t hit it hard enough to break through the end of the battery, or crush the cap.

Step 3: Place the Battery on a Stack of Magnets

Picture of Place the Battery on a Stack of Magnets

Place the battery on top of a stack of small neodymium magnets, stacked high enough to leave a surface for the wire to contact.

Step 4: Prepare the Wire Coil

Picture of Prepare the Wire CoilPicture of Prepare the Wire CoilPicture of Prepare the Wire Coil

Inspect one end of the wire, and if it’s cut flat, cut it on an angle with wire cutters, or a multi-tool, to sharpen the wire to a point.

Using the sharpened end as the beginning, form a vertical loop, then begin forming the shape of a spiral. Form the coil either clockwise or counterclockwise, and make it two to three times the diameter of the battery, finishing off the loop in a smaller diameter.

Place the pointed end in the dimple at the top of the battery and if the coil is too short, or too long, you can stretch or squeeze the coil until it’s the proper height.

Let the coil hang freely and see if the free end of the wire contacts the magnet below the battery.

If it does, a current will pass through the wire, and if the wire has a light enough contact with the magnet, the wire will begin to move, either clockwise or counterclockwise, depending on the polarity of the magnets.

Step 5: Watch It Spin!

Picture of Watch It Spin!
Picture of Watch It Spin!


If the coil does not move, you will have to adjust the balance of the coil by tweaking the shape of the bottom of the coil, or move it closer to the center of gravity, or further away, until the hanging wire gently brushes the surface of the magnet.

Once this balance has been achieved, the motor will begin to rotate.

By reversing the polarity of the magnet, by flipping it over and placing the battery on the opposite end, the motor will change the direction of rotation.

One direction of rotation or the other could work better to make the motor spin, and experimentation will show the best way to place the magnets. With a well balanced coil the motor should work fairly well in either direction.

Note: The battery will heat up if the motor stalls as it then becomes a direct current short circuit. Also, if the motor is running for too long the battery could heat up. Please monitor this experimental motor carefully.

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