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Project Notes

#203 HomopolarMotor

Build a basic homopolar motor.

Here’s a quick video of the circuit in action:



The homopolar motor was the first electrical motor to be built. Its operation was demonstrated by Michael Faraday in 1821 at the Royal Institution in London. It is also the operating principle behind railguns!

The basis of operation is pretty simple, once you understand magnitic and electric fields - which back then was really the edge of science.

The homopolar motor is driven by the Lorentz force.

The current from the battery flows through the wireframe. This intersects the magnetic field of the neodynium magents which is roughly perpendicular. The right-hand rule simplifies the understanding of the resulting force, which causes the motion.


Scam Alert

There are lots of demonstrations that claim “free energy”. Unfortunately, there is no such thing. Electrical potential of the battery is consumed in running the motor. Although it may not seem like it at first, the wire frame actually (intermittently) completes the circuit from positive to negitive of the battery, establishing the electric field. In fact the demo video shows how easy it is to deplete a battery in such a configuration!


The Build

Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.