The Lenz's Law Guillotine demo

[andrewtretiakov]

Hi all,

We made this recently as a demo for our students and outreach events. Based on a US design we decided to build it using wood, aluminium plate with fixed neodymium magnets and a copper plate 'blade'.
We can demonstrate eddy currents, Lenz's law, magnetic braking, etc.

It really looks fantastic!

Enjoy:
https://youtube.com/shorts/NMz7Ua5HgRs? ... JI9ox3Ad2y

[MarbsLab]

You can also leave out the magnets for students who behave badly

[andrewtretiakov]

You can also leave out the magnets for students who behave badly

Hahaha! If only

[lemmi]

Hmm, the effect depends on the induction of current and therefore a magnetic field in the falling guillotine. This is independet of the magnetic qualities of te metal used for the guillotine blade. It should be made clear in the video, that the blade is not made of iron, which by itself could be attracted - and its falling velocitiy therefore diminished - by the magnets. Or, perhaps it is?

[mgritsch]

It should be made clear in the video, that the blade is not made of iron, which by itself could be attracted - and its falling velocitiy therefore diminished - by the magnets. Or, perhaps it is?

The effect is not depending on magnetic properties, but strongly depends upon the conductivity of the metal. Poor conductivity limits the eddy currents and therefore the strength of the opposing field. A blade made of iron may therefore be even much more dangerous than one made of copper! Even with Al vs Cu the difference is already clearly visible.

[lemmi]

EDIT by lemmi: aus der Artikelschmiede hierher verschoben