Magnet Car




Introduction: Magnet Car

About: We are a supplier of neodymium, rare earth magnets. We also love to conduct experiments with our magnets and build unique projects with them! We have several engineers on staff who are always thinking of new...

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

As previously mentioned, you only need three things to complete the project-- a few magnets, a AA battery, and aluminum foil.

We use a total of 3 magnets:

-One R841 magnet

-Two RX032 magnets

-One DC2 magnet (optional) if you want to make your car go in circles.

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.



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    44 Discussions

    How can the same poles be facing outward on the ends of the battery?

    Then the same poles would be facing inward. Wouldn't the magnets repel each other and not stick to the battery?

    I've also tried this numerous times in many different ways and could not replicate the results.

    I tried, KJ - thin foil, flat. Just very anemic result.

    1 reply

    We are sorry to hear that! It did take us awhile to get it to work well, remember to change out the batteries frequently. Also, make sure the battery is centered on the magnets. Centering the battery might be one of the most important factors.

    Just a lowly physician here, but I had the same sad results. Very disappointing for the grandkids. I bought the magnets directly from K & M.

    I did several test. None of which yielded the results in this video. I doubt it works. My batteries overheated. I changed polarity of the magnets, did multiple flat surfaces all to no avail . I have the exact magnets used by the author. I posted to my YouTube as well. I do have an electronics eng degree so I know a thing or two about this. Physics in my universe are apparently different .


    2 years ago

    this is a much more fun use for the homopolar motor than making spinning structures (not that that is boring, people have done some amazing things with spinning wire).

    5 replies

    Thank you for this post Laral, You have made me known this interesting site and now I published my first Instructables on that experiment

    I did? How'd I do that? BTW, awesome idea that really works well! I'm glad you made an Instructable about it.

    I haven't seen this before. I had a teacher with a similar setup (it was not a homopolar motor but otherwise identical), and I don't think I would have ever thought to do this. I have also seen a setup that had "gears", it was able to spin at different speeds.

    It was probably a Mendocino Motor. I have seen these before but I too never saw one with a homopolar motor.

    my video post didn't take, not sure why. So this is what is going on: This can not work. You are shorting across positive and negative leads of the battery. Motors require brushes, stator and rotor , the intermittent current connection in the coils in rotor creates a magnetic field that is affected by the permanent magnets on the outer housing ( assuming the simplest motor design ) if you change the polarity the motor will spin the opposit direction . Think about North and South ends of a magnet. If I take two magnets and put south to south what happens? Consider the law of charges , opposites attract , take a comb, swipe it through your hair a few times , cut up some pieces of paper in to tiny pieces and hold the comb close to those bits of paper. See what happens ? ...this video reminds me of the one where the person claims they can take a glass of water and make it stay after removing the glass by twisting it. This is not going to work . Sorry if I bursted the bubble here.

    2 replies

    We have seen many of these fake videos as well, claiming they can do something. We get contacted about many of them, since many have to do with perpetual motion. We were skeptical about this one as well, but it actually does work. It is basically a homopolar motor. If you read our explanation how it works, you'll see why! Also, check out our blog article on a Homopolar motor for futher explanation.

    sorry, I tested this every way possible and achieved no movement other than acting on it with external forces. Though I did post a working Homopolar motor that does support theory and application . It took me about an hour just sitting in my living room fumbling about and I made that work. Your neodymium magnets are quite useful btw , I plan to use some ring magnets of this type in a device I am building that disables any and all electronics using radio waves and skin effect . I of course can not specify how that device will work any further however strong focusing magnets are needed.

    You are is a short circuit! The batteries will not last long for this type of thing, but they will work for a short period of time. It is not a very practical project, but it is a cool variation of a Homopolar Motor. There is flowing current in one direction, through the battery through the foil, back through the other battery. There is also a strong magnetic field present. Lorentz Force takes effect here...a flowing current in the presence of a strong magnetic field will exert a force 90 degrees to the direct of current flow and magnetic field (Fleming's Left Hand Rule). Because the magnetic field is facing the same way on both ends, the force from each is in the same direction.


    2 years ago

    I tried this with N40's, and got absolutely no effect at all. I will have to wait and try n42's when I get some.

    1 reply

    There are a few variables with this! Make sure your surface is perfectly level. These cars don't have much force, so they won't be able to make it up even the slightest incline. Also, make sure to use the thinnest aluminmum foil you can!

    also, be aware, it doesn't matter what magnet you use, you are still SHORTING ACROSS THE POSITIVE AND NEGATIVE LEADS.

    Could you please post a link where you can get these magnets in India?