BUILD A SIMPLE ELECTRIC MOTOR (HOMOPOLAR MOTOR)
This is a project that I have been wanting to try for some time, so when it came up in our science book, I decided to go for it. The boys and I have been learning about magnets and electricity using Exploring Creation with Chemistry and Physics. I totally recommend this series! It’s perfect for doing science with kids of multiple ages together.
Want to see the motor in action?
Safety Notes: This electric motor project is great to do with kids. Young kids won’t be able to make this, but they will love watching! Kids ages 8+ will be able to help, although adult supervision and help will be needed. My 12-year-old could do this on his own, but supervision is still needed. Neodymium magnets are extremely strong and should only be used under supervision and should never be used with kids who might put them in their mouths. Also, the copper wire may become hot, so be aware.
To make your motor, you will need:
- One AA Battery
- Copper Wire – We used 18 gauge
- A neodymium (rare earth) magnet – We used two of this size of neodymium magnets
- Wire cutters
- Needle nosed pliers
For the optical illusion version:
- Index card
- Colored pencils
First, cut a section of wire 7 inches long. Bend a small loop in the wire in the center as shown below.
Then bend both sides down. Attach your magnets to the negative end of a AA battery.
Now bend each of the ends as shown. You need the both ends of the copper wire to gently touch the magnet.
It will take a little bit of work to adjust the copper wire so that it touches the top of the battery and both ends touch the magnet. The copper wire Once you have it just right, the wire will begin to spin!
Try flipping the magnets over and watch what happens to the direction of the motor. When you reverse the poles of the magnets, the motor will spin the other way! So cool.
Why does it work?
This motor is called a homopolar motor, and it was first demonstrated by Michael Faraday in 1821. This motor works because of the electromagnetic force, called the Lorentz force. A basic definition of the Lorentz force is the force exerted by a magnetic field on a moving electrical charge. You can read more about it here. A simplified explanation is that electricity flows out of the battery, through the copper wire, and into the magnet. The magnet sends an electrical charge through the other side of the wire and back to the battery, completing the circuit. The wire and the magnet both have electric fields around them, and these fields repel each other, exerting a force on the wire causing the wire to spin.
Here is another article about homopolar motors if you want to learn more.
Try making it an optical illusion!
After we got our motor working, we decided to make another one with an optical illusion! I cut another piece of wire about 10 inches long and cut off the extra ends when I was finished shaping it. After making the loop in step 1, I bent the wire up to give me something to tape an index card to.
Then I drew a fish on one side, and a fishbowl on the other side
Make sure not to let the tape cover the wire loop – you’ll need for that to touch the top of the battery.
The motor spins a little more slowly because of the added weight of the index card, but it still looks really neat!