Intro: So I know what your thinking, what on earth is a homopolar motor! Before I can show you how to make one of these simple and fun to watch motors' you might want to know what it is and how it works first, right?
How it works: The homopolar motor is driven by the Lorentz force: as it moves through a magnetic field, the conductor is pushed through a magnetic field by opposing forces. This force induces a torque around the axis of rotation. Because the axis of rotation is parallel to the magnetic field, and the opposing magnetic fields do not change polarity, no commutation is required for the conductor to keep turning.
Brief History:In 1821, soon after the Danish physicist and chemist Hans Christian Ørsted discovered the phenomenon of electromagnetism, Davy and British scientist William Hyde Wollaston tried, but failed, to design an electric motor. Faraday, having discussed the problem with the two men, went on to build two devices to produce what he called "electromagnetic rotation". One of these, now known as the homopolar motor, caused a continuous circular motion that was engendered by the circular magnetic force around a wire that extended into a pool of mercury wherein was placed a magnet; the wire would then rotate around the magnet if supplied with current from a chemical battery. These experiments and inventions formed the foundation of modern electromagnetic technology.
Materials needed: Copper wire, Double A battery, 1 half inch diameter cylindrical neodymium magnet, Needle nosed pliers, and a wire cutter.
Step 1: Get the Materials
Before you can start making a homopolar motor you need a double A battery, Copper wire (The thicker the wire, the slower the motor will go), Neodymium magnet (also known as "rare earth magnets"), Needle nose pliers, and a Wire cutter.
Step 2: Cutting the Copper Wire
Using your wire cutter carefully cut a piece of copper wire about 12 inches long. The more copper wire you cut the bigger and slower the rotations you will get from your homopolar motor. The less copper wire you cut the smaller and faster rotations you will get from your homopolar motor. Make sure that you cut the wire cleanly so you wont have to worry about a sharp point.
Step 3: Pinching the Copper Wire
Using your thumb and index finger, squeeze the two ends of the copper wire together. While squeezing the copper wire, put your other index finger in the wire loop and move your finger towards the middle of the other end of the wire and push until you get a shape similar to that of a narrow triangle. Release your grasp of the two ends. Now at the tip of the copper wire use your needle nosed pliers to pinch the wire tightly together.
Step 4: Straightening the Copper Wire
Using your needle nose pliers clamp down right next to the pinch you just made and bend the wire counter clockwise about 90 degrees. Do the same for the other side of the pinch.Don't worry about getting a perfectly straight angle as we are about to bend the same wire anyways.
Step 5: Bending the Copper Wire...again
Using the needle nosed pliers about 1 to 2 inches from the pinch bend the wire counter clockwise to about 90 degrees. Do the same for the other side of the pinch. Try to keep one side the same length as the other side.
Step 6: Attaching the Magnet to the Battery
The title says it all, all you have to do is attach the magnet to the battery. This is the easiest step put the next step is going to be the hardest.
Step 7: Fitting the Copper Wire to the Magnet and Battery
Near the edge of a table balance the pinch on the top part of the battery in the middle. The ends of the wire should be hanging over the edge of the table. Note where the wire is near the middle of the wire. Using your needle nosed pliers bend the wire towards the battery about 90 degrees where you noted the wire. Make sure that the wire is crossing horizontally against the middle of the wire.
Step 8: Cutting the Excess Copper Wire
Using your wire cutters cut the wire where the wire protrudes from the box like shape. The remaining shape should be close to a square.
Step 9: Curving the Wire Around the Magnet
Place the bottom of the square shaped wire on both sides of the magnet. There should be one side of horizontal wire on each side of the magnet. Using your hands curve the horizontal wire around the magnet. Too tightly and the wire wont spin well, too lose and the wire wont go fast enough.Cut away the excess protruding wire from the curved side of the wire.
Step 10: Placing the Wire on the Battery and Magnet
Place the curved part of the wire through the battery all the way until the pinch is touching the battery. Center the pinch in the middle of the wire and the curved wire around the battery. Now all you have to do is give the wire a little push and your motor will be running! The wire will accelerate fast around the battery and the magnet. Amaze family and friends with your motor. Have fun with your motor and feel free to comment and vote!