Posts Tagged‘current’

The Tiniest Electric Train.

I’ve never really been one for trains, neither those that serve as public transport or their diminutive brethren that grace the basements of many, but the technology behind some of them is quite impressive. Indeed you can’t go past the Shinkansen of Japan, trains that are so fast that they regularly compete with airlines for the same passengers and have recently achieved astonishing speeds. However beneath all the technical wizardry that powers those impressive machines lies some incredibly simple physical principles, ones that can be replicated with some copper wire, a couple magnets and a battery:

The way it works is incredibly simple. The “car” of the train is made up of a couple high-strength magnets that are oriented in the same direction, ensuring that their magnetic fields flow in the same direction. Then when the car is placed onto the track ¬†of coiled wire they help complete a circuit with the coil of wire around it. This then creates a magnetic field around the car and the resultant force between it and the permanent magnets results in a force that’s vectored forward. However the time it will be able to do this is limited however as the creation of the magnetic field consumes power from the battery. Most estimates online have the run time somewhere around 30 minutes or so from a typical alkaline AA battery.

Indeed one interesting thing about this train is that it relies on the high internal resistance of regular alkaline batteries to function properly. You see a typical battery has what amounts to a current limiter inside it, preventing anything from drawing current too fast from it. If they used say a NiCd style battery, which has an incredibly low internal resistance, I can see the results being either much more spectacular (like the car flying around the track) or catastrophic (like the battery overheating and the wire melting). Actually now I’m kinda curious about what would actually happen.

Now where’s that old battery charger of mine…