Here is a quick, easy way to create a self-propelled car using simple household items! All it takes is some magnets, a AA battery, and some aluminum foil!
Step 1: Find the Supplies
Step 2: Place the Magnets on the Battery
In this series of pictures, we show putting the magnets on the battery. We first place an R841 on the positive side of the battery. This helps the bigger RX032 magnet make better contact and helps it stay centered.
Then, place another RX032 magnet on the negative side. You want to make sure the SAME poles are facing outward on both ends. You can do this using the method seen in the video!
Step 3: Layout Aluminum Foil and Have Fun!
This step is pretty simple...lay down some aluminum foil and place the magnet car on it to watch it propel itself! We found that cheap, thin aluminum foil worked best. The thicker, more expensive stuff was harder to get the imperfections out of and the magnet car had trouble navigating over the rough terrain.
Step 4: Technical Info: What's Happening Here?
This setup provides the two main ingredients of an electric motor: A flow of electric current and a strong magnetic field. We get electrical current because there’s an electrical contact between the battery, through the magnets, through the foil, through the magnets on the other end, and back into the battery.
If you think this looks like a short circuit, you’re right! This car runs the battery at higher currents than you're supposed to. You’ll use up batteries quickly doing this demonstration. After a few minutes of using one, you might find that the battery is too weak to continue.
The magnets are arranged with the same poles facing out. This provides a good magnetic field that’s in a uniform direction across the length of the foil (under the battery). Thus, the current is flowing through a place where there is a strong magnetic field.
For more scientific detail, our article about Homopolar Motors has a pretty good breakdown. If you have an electric current going through a conductor that happens to be in the presence of a magnetic field, you’ll feel a force on that conductor. The pictures there show an example with an actual wire, though in this case we’re running the electricity through aluminum foil. The principle is the same.