[Amazing Science’s] Simple Electric Train

Making an electromagnet is as simple as wrapping some wire around a nail and taping the wire to both ends of a battery. When you’re done, you can pick up some paper clips – it demonstrates the concept well, but it could use some more oomph. [Amazing Science] has done just that, making an “electric train” (YouTube link). All that’s needed is some coiled copper wire, a battery and magnets thin enough to fit through the coils. The magnets snap onto both ends of the battery. Put the battery inside the coil and watch the fun! The electromagnetic force generated by the current moving through the coil pushes against the magnets attached to the battery, pushing the battery along the way.

[Amazing Science] plays with the setup a bit. Connect both ends of the coil together and the battery will travel in a loop until it’s drained. Add a small hill, or even another battery/magnet set to the mix, and watch them go! We may even make a version of this ourselves to take with us to family gatherings this holiday season – it’s simple, fun, and can teach the young ‘uns about science while we swig some egg nog.

[via Reddit]

106 thoughts on “[Amazing Science’s] Simple Electric Train

  1. OK, I’m stumped. It’s been a “few” years since I’ve had Physics 201 so I’m a bit rusty. Does the battery have anything to do with the motion other than acting as a spacer between the two sets of magnets? There’s no circuit for the current to flow thru unless the magnets are conducting the electricity to the coil thru physical contact.

    1. Ahh but you missed a detail…

      The wire is bare copper, hence the circuit is created by the magnets and the local wire around the battery between them becomes the electromagnet.

      This is a very cool demo of Electromagnetism! Probably the coolest I have seen by far except those involving plasma and electron beams…

    2. Think of it this way, do perpetual motion machines exist?

      The answer is of course no, so where is the energy for this coming from? Must be the battery!

      Also the clue is in the title, “electromagnet”.

      The current flows through the battery into the magnet into the coil surrounding the magnet. The magnets are set up such that the changing field in the coil pushes them forwards.

          1. Never understood it either… I mean, we have science fairs here but there is not such a thing as winning the fair. And even when there is a bigger fair to which feel projects need to be selected, the projects aren’t selected with all the other competitors around.

    3. You answered your own question. The wire is not enameled, so it becomes part of the circuit using the magnets as the contacts and the battery for power. It is a self powered solenoid.

    4. Yes, you’ve got it. The coil is bare wire and the magnets are the conductors. Notice how the battery doesn’t move on its own until the trailing magnets touch the coil, and how the battery stops when the lead magnets exit the coil.

    5. Pretty easy concept, the battery has two neodymium magnets connected to each terminal. When you insert the battery into the cooper coil, current will flow from one of the battery terminals around the coil into the other terminal; this creates a electromagnetic field that is always localised between the battery terminals. Now, because you actually have permanent magnets attached each end of the battery, the magnets react to the magnetic field making the whole attachment move.

  2. Winding the coil is the tedious part, but I think I may do this with my daughter over Christmas break. We always have a train under the tree, but now we can make our own! Too bad there’s no BOM. While it looks like a standard AA battery, and then the coil is sized appropriately, what’s the source for the magnets? I guess some detective work is part of the fun!

    1. The Coil is solid core bare copper or other wire. Important part is that it does not have insulation. It looks like the batteries are those 12V Garage Opener and Car Alarm remote batteries. There are tons of places online that sell magnets, and many craft and hobby stores sell them too. Look for small neodymium disk magnets that are polarized on the flat faces. Solid core wire can be found at your Local Home improvement store in the hardware section, usually for hanging pictures and other odd jobs. You could also use jewelery making wire from a local craft store i would bet.

      Im pretty sure a quick amazon search will get you everything you need to build this. The diameters are not critical, as you can wind the coil to s suitable diameter to fit the magnets you can get. The smaller the diameter, the longer you will be able to make it. I’m betting the effect is more pronounced as well.

    2. The way I read that it seems like you want to replace the train around the tree with this? Unfortunately it’s probably a fire hazard being it follows the same principles of a homopolar motor making that battery under a constant short. If you ever made one the batt gets hot as hell and usually runs a good 10-20 min which would closely apply to this setup as well.

      1. I don’t propose winding a coil “track” long enough to go around the tree, just mentioning that given prior experience with trains being a Christmas seasonal thing it would be an appropriate time to do this with her. Plus my son will be home from college and they might enjoy doing it together.

  3. But if the wire is bare, you have to stretch the coil some so the turns aren’t shorted out. The description makes it unclear that only a portion of the coil is energized as the battery moves along. I would think the magnets have to be bigger in diameter than the battery to maintain contact, and even then it would be iffy.

    1. electromagnetism

      the power flows through the magnets to the copper coil, that forms a electromagnetic field the two magnets groups on either side of the batter. that field pushes against the Neodymium Magnets on the battery moving it forwards,

      hope that helps

    1. Not enough time for Christmas 2014, and if you’re going to do a Kickstarter then you’d better supply pre-coiled “track”, not raw copper wire, and that’s going to take some lead time to set up, probably with a Chinese supplier.

      But if you do it I’ll place an order.

    2. No, I’m sure first we’ll see a kickstarter claiming to have over unit gain electric power generation using this setup. “It is nearly working; I just need $5000 more to build a working prototype!”

  4. “..and can teach the young ‘uns about science..”

    Probably just teach them they need more batteries. Unless you’re going to haul along a whiteboard or two (or a power point presentation on a tablet) and delve into the actual physics, demos like this do little to further anyone’s education that doesn’t already understand the basics of the demo.

    “look isn’t that cool” – SHHHHHHHHH, the Commercial is over, be quiet the games back on.

      1. I’ve done this with something like 1/4inch ID copper or Al tubing and a 1/8inch diameter magnet. It’s not as impressive, but it is noticeable. (I’ll also point out that a large supermagnet as shown in that video is pretty dangerous, as well. It’ll smash body parts in its joy to find magnetic partners.)

  5. I may be wrong, but with such a low resistance in the copper, could this potentially explode a battery if it runs too long? or is the load resistance from moving the battery enough to lower the current to a safe level? I suppose the loose contact would also drop the current a bit. I’m a noob when it comes to electronics but I’ve learned a bit about battery safety from vaping lol.

    1. I won’t say it’s impossible, but zinc-carbon and alkaline cells can handle /some/ abuse before exploding. I had an alkaline cell explode once – i inserted it wrong way round, and 1,5a of current was running through it – so it was effectively being charged. It popped after about 10 minutes of that kind of abuse, splattering some boiling hot electrolyte in a circle of 30cm. They can handle a normal 1,5a current draw just fine, and i think the contact resistance between magnets and copper limits the current to a fairly safe level.
      Shorting them out would probably not result in the battery exploding – but they might vent and leak if they get too hot. They won’t explode without getting hot, so you have some indication about whether you’re safe or not.

  6. I made one this morning (sorry, no video. too lazy). Used about 15metres of copper wire ripped out of some leftover building mains wire. Coiled it around a wooden dowel on my lathe (could have used a cordless drill too). 4x 18mm diameter neodymium magnets and an AA cell. Works like a charm.

    1. Yes, yes they can! NiCd/NiMH will be able to supply enough current to heat the wire coil quite a bit. It should go a LOT faster, but will need careful testing to avoid overheating the battery. May also spot weld the magnets to the coil.

    1. It’s the essential idea behind how this works, I think. Magnetism and current are sides of the same coin. The battery makes a current that makes a magnetic field that pushes the magnets. But the magnets make a current in the wire that resists the battery. You can’t have one without the other.

  7. Lots of fun there. Just don’t blow up the battery! Basically they are operating into a short. I would like to see a little chopper circuit made the size of the cylindrical battery to switch at a few kHz, but DC and see if it makes it more efficient and get the current draw down. Most of it is probably wasted as heat from the internal impedance of the battery. Try to shift the consumed energy into the static load of the coil, and the dynamic load of the moving magnets…..

  8. Magnets aren’t that expensive. I buy mine from KJ Magnetics .com. I have a 2″ diameter copper pipe that’s about 3 foot long. The kids are amazed when it take 10+ seconds for the magnet to fall through. It’s a great demonstration of Lenz’s law.

    You can pick up the wire from most hobby stores in the U.S., just make sure it’s bare copper. You can get the batteries at walmart.

    Keep in mind the copper will get warm after a while as you’ve got a direct short on the copper, albeit for a short period of time. If the battery gets stuck you could have a problem. Just something to keep in mind.

  9. A really interesting demonstration of electromagnetism and this is how it works:

    A circuit is formed between the ends of the battery and the part of the coil within the ends of the battery. This turns the section of the coil into an electromagnet, which is aligned with the permanent magnets.

    The permanent magnets at the ends of the battery have their North poles pointing in opposite directions. So, the permanent magnet on one side of the battery is sucked into the electromagnet and the magnet on the other side is pushed out. This results in a net force acting on the battery and permanent magnets, which causes motion.

    Dr Andrew Ferguson
    Philip Leung
    Maude Gibbins

  10. wow man! just wow!
    just HAD to watch twice XD

    unless im mistaken, neodyminum magnets dont take heat very well. i lost one due to heat (i think) so the fact that this setup works more then once means that the magnet is NOT getting that hot. its the heat that causes the battery to explode.

    not sure about nimh but nicd would just melt the wire and destroy the neo magnets.
    the alkaline batterys have enough resistence to allow the setup to work without eating itself.
    as for the contact resistence? probably as high or higher then the battery. the arcing/flyback also might be bad for the battery/wire/neomagnets but is apparently okay. lithium might be extremely dangerous!

    1. Yeah, they suck horribly in the heat. I bought some cheap magnets off amazon and they permanently demagnetized in my car during a single summer day. Car was parked under a tree, no direct sunlight on the magnets.

      There are higher grades of magnet that are more heat tolerant (like, less than boiling water tolerant for most of them), but they’re pretty much impossible to order in anything other than custom made 10k+ quantities

  11. Doing this for a science project and we made the coil. We used copper magnetic wire for this. We also tried 3 different batteries. AA, AAA, and A23 size. We used the magnets suggested. We have tried also 2 different sizes of wire spoolled around two different size dowels. We had no luck in getting it to run or move for that matter. Any ideas as to why? Would love any suggestions. Thanks!

    1. Copper magnet-wire is coated with insulative-paint so it doesn’t short-out with itself where the windings touch… you need copper wire that’s *not* insulated, and need to make sure those windings are separated by air. Not sure what the best source for this would be… is there such thing as copper picture-hanging wire?

      1. (solid, not stranded, since stranded-wire would probably not hold the shape). The point, in this project, is that the magnets conduct electricity into the wire, where it touches the wires. Then the section of the coil *between* the magnets (the windings surrounding the battery) turn into a magnet. It can’t do that if there’s no conduction because there’s insulation between the magnets and the coil :)

        1. Thanks for the help. We have found bare copper wire but we only get little movement not like the one shown in the video. We added two magnets at each end on the AAA battery and wound the bare copper wire in a coil. For some reason we don’t have a lot of movement. Is it possible that there isn’t enough magnets on each end so there isn’t enough pull? Or how tight does the wire coil need to be? Is it so tight with very little breaks or more loose with no coil touching each wrap? Any help would be great. :)

          1. Anyone else able to answer these questions? With all these comments, I can’t be the only one getting emails…

            Sorry, Brandy, I can’t answer from experience… the insulated-wire thing was a sure-thing, but I haven’t actually built one. Someone else in the comments claims to have done it, with a AA, so a AAA seems like it should work as well. The one thing that comes to mind is the magnets might be in opposite directions and fighting each other…? Try flipping ’em around on one end and see what happens. My guess is the coil should definitely be wider in diameter than the battery and magnets, so it doesn’t snag. The wraps shouldn’t touch each other in too many places, ideally not at all You can see the pictures, it’s not like they’re exact-spacing. It might also matter *which way* the magnets are oriented… they *definitely* have to be in the same direction… there are only two possibilities, try ’em both. Snap all the magnets together, then use a marker to mark the same side of each one, then try with the marked side connected to the + battery terminal and the unmarked side connected to the – terminal, then swap ’em and try again.

          2. How much current is flowing when you short the battery (via the magnets) through a current meter? It should be several amps, but don’t keep it on for more than a second or two ha ha. (Put your cheap supermarket multimeter on the maximum current range – mine is 10 Amps). If there’s no current, what about straight from the battery terminals? If there’e still no current, the battery is flat.

            Is the surface coating of the magnets conductive? Check it with your multimeter on the continuity / beeper setting. Some have wierd coatings.

          3. I built a working model yesterday, Things I found are as follows: speed directly relates to the number of turns per inch. If it is moving slowly, your coil is too loose. Also, make sure you have good contact between the battery and your cells. I ended up using a disc shaped magnet, stuffed with tinfoil, on the button end of the battery, and it improved the performance significantly. I’m not sure on this part, but if I put the magnets on the positive side, and then let the negative ones jump onto the negative end, I needed to flip those magnets. The rest of my setup used what has already been described: 18awg bare copper wire, wrapped around half inch dowel, with half inch neodynum magnets on each end.

    2. Hi. We used bare copper wire (18 gauge) wrapped around a 1/2 inch wooden dowel. Three 0.47″ neodymium magnets on each end of a AAA battery (AA won’t fit if you use a 1/2 dowel), and it worked! Now – I have a question – we tried one of those 12 volt A23 batteries, expecting more ‘zip’ from the higher voltage (vs. 1.5 V with the AAA) …. and the 12 V battery didn’t work at all! Any thoughts as to why this might be? Thanks!

      1. intriguing, if you find out, post it here? Only thought I can come up with is that such a small 12V might have a high internal resistance, so can’t pump out the current. Measure the voltage when the coil’s attached?

  12. We have volts starting at 1.5 for a AA as well as a AAA. Once we do the charge and add the magnets we have a charge drop to 1.33v. For each battery. We also have been able now to get a AAA battery fully charged with 4 magnets like shown in the video on each side. When I put in the bare copper coil we get a lot of vibration and spark but still ok major movement. Still haven’t an idea as to why we aren’t moving.
    I was able to do the simple motor with two magnets, a battery, and bare copper. It did a lot of spinning so I know I’m good on a charge. Thanks for helping. ;)

  13. Tried to make this with left over 14 GA copper wire that I used to make homopolar motors (used 1/2 in pvc pipe to help coil), AA battery, and first 2 neodymium batteries on each side and then tried 3on each side but had no luck. Now my motors spin great! What am I doing wrong?

  14. I can’t get my train to work! I’ve switched the magnets back and forth and triple checked my materials (AA battery, bare copper wire, and neodymium magnet). I’ve done the idiot self check and it appears I’m the only one that doesn’t get it. Why can’t I make this work????

  15. My son is doing this for a science fair. He is stumped on how to graph his data though. He did 3 trials each of different configurations: 2 magnets on each side, 3 magnets, 4 magnets. Then he timed each one 3 times as it ran through the coil. How would you set this up as a graph?

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