Faraday’s Law Of Electromagnetic Induction

Faraday’s Law of Electromagnetic Induction

The ball (also a magnet) is falling quite a bit slower than expected (despite the slow motion). This can be attributed to Faraday’s Law:

When a conductor is exposed to a changing magnetic field there is a current created within the conductor. Or more technically a magnetic flux changing over time produces an electromotive force across a conductor.

That’s not the whole explanation though…

Lenz’s Law

When the magnet is falling the current in the cylinder is producing a magnetic field as well. Lenz’s Law states:

 The induced current will produce a new magnetic field that will oppose the change in magnetic flux.

The produced field applies a force to the magnet resisting its fall. If the tube is long enough the magnet will reach a constant velocity because the magnetic force and weight will cancel each other out (no net force).

This works like air resistance on a falling object. Eventually the resistance completely counters the gravitational acceleration of the object.

Faraday’s and Lenz’s Laws basically tell us that the faster the magnet moves the more the conductor (tube) will resist the magnet’s fall.

Watch this Veritasium video on the same concept and see this phenomenon in real time.