The DIY Electric Train is amazing fun, easy to build, and a wealth of science that can be discussed at many levels. It does take a bit of concentration and a few key tips to make it work, which is why we put this at the 4th grade level.
But you be the guide. The more you want to help in its construction, the younger the student can be.
… and the deeper you want the student to get into the “why it works” part, the older they can be.
This featured video was created by “The Bearded Science Guy” and he does a nice job of introducing the topic at the middle school level.
So How Does The DIY Electric Train Work?
As was seen at about the 0:45 mark in the video, the “train” components from left to right were positioned so that we had a S pole then N pole for the 1st magnet, a S pole then North for the battery itself, but the last magnet was opposite at N then S pole.
When the “train” is placed into the coil, because the magnets are actually touching the copper wire, electricity from the battery flows through the magnets into the coil. When electrons flow through a coiled wire, that induces a magnetic field. And that magnetic field has polarity as well.
Because of the way the batteries are positioned, one end of the train is attracted (or pulled) by the coil’s induced magnetic field and the other end is repelled (pushed) by it.
But that only works if you put the right end of the train in the coil. If your first attempt does not work, just turn the train around and try again!
Other Things To Do
Coil separation, or the spacing between the coils matters and I recommend you test that to see how. If you make them too wide, then the coil’s magnetic field isn’t as strong and the train moves slower. Too tight such that the coils touch and the same thing happens. But something in between (like in the above video) works really well. Test this!
The type of magnets on the end can change things dramatically. Not all magnets are equal and “normal” magnets like you might use on your refrigerator won’t work. You need the new rare earth super magnets (neodymium magnets as noted in the video) for the project to work. The “old” magnets just don’t have enough strength.
The super magnets come in various “n-number” strengths up to n52, but n48’s work pretty good if you are using AAA batteries (and they are cheaper).
The number of magnets are also important. The more you put on (one would think), the more magnetic strength you have and the faster the train will go. Or will it?
Yes it will, up to a point. Once the magnets get too heavy then friction starts to slow things down.
If you want another source that discusses in detail how each variable affects the outcome, you can look here.
But I think it is more fun to try it and see for yourself … then try to figure out why.
Need More Detail For Older Students?
The above is a good start, but we really didn’t talk about how a magnetic field is induced in a wire, and we didn’t discuss how you can predict which direction that field will go in and just how that interacts with the “train” to be sure it will move through the coil.
We didn’t define how much current will be provided by the battery and we did not calculate field strengths.
We didn’t use right hand rules … in other words, there is a LOT that can be done to turn this simple, fun and entertaining experiment into a head scratch-er for high school science students!
After riding the rails with this one, take a look here for a simple but fun project: https://how-things-work-science-projects.com/lemon-battery-project/