A Faraday disk built to learn about electromagnetism and early generators.
Write up with some concepts, equations, and math is located in faraday-disk.md
At around 200rpm, the generator produces voltage of around 1.9-2.1mV and current of 0.1μA. Theoretically (no losses), with this design I should have gotten 0.18V and 0.8007A.
As expected, this generator performed far from ideally.
I think most of the loss comes from brush contacts, oxidation on the copper disk, and the effects of eddy currents.
- 6mm (606) bearings (x4)
- 6mm axle, ~120mm
- 6mm axle, ~180mm
- Stranded wire for brushes
- 40x20mm neodymium magnets (x2) (amazon)
- Copper foil (for continuity between disk and axle)
- 150mm copper disk (amazon)
- 3D printed parts
- cad/axle-2-support.stl
- cad/axle-cap (x2)
- cad/brush-mount-bolt.stl
- cad/brush-mount-bottom.stl
- cad/brush-mount-nut.stl
- cad/coupler-bolt.stl (x2)
- cad/hand-crank.stl
- cad/magnet-brush-mount-large-lid.stl (x2)
- cad/magnet-brush-mount-large.stl
- cad/spur-gear-11.stl
- cad/spur-gear-44.stl
- cad/stand-left.stl
- cad/stand-right.stl
- Various m3 bolts, nuts, and washers (lost track while building and redesigning...I'm dumb)
- https://en.wikipedia.org/wiki/Homopolar_generator
- An Introduction to Classical Electrodynamics by Keohane; Foy
- University Physics with Modern Physics (14th Edition) by Young, Hugh D.; Freedman, Roger A.
- The Homopolar Handbook by Valone, Thomas
- The Unipolar Generator: A Demonstration of Special Relativity, Berg; Alley
- https://en.wikipedia.org/wiki/Classical_electromagnetism_and_special_relativity
- Unipolar Induction A Messy Corner of Electromagnetism, Härtel
- Notes on a Unipolar Dynamo, Tesla (1891)
- Untried Homopolar Generator Experiments, Beaty
- https://en.wikipedia.org/wiki/Faraday_paradox
- https://en.wikipedia.org/wiki/Eddy_current
- The Feynman Lectures on Physics, Volume II, Lecture 17