faraday generator

[Artic_Knight]

ok i had a half baked idea and im sure someone has tried it but i dont have the resources to do so myself.

if you take 2 flat copper disks and attatch magnets to them and spin them they generate electricity per faradays invention. what is the resistance generated? lets say you have one motor that is spinning one coil through a magnetic field there will be resistance put on the motor from the magnetic feild but when the magnets are moving with it attatched to it, what is to create resistance now besides the simple weight of the object which is less friction than moving through a magnetic field? has anyone seen if they could make a self sustained device from this? a generator?

[BEP]

You've asked one of the favorite questions!

I'll give you the usual two answers.

1. (My understanding) Just because the magnet is spinning with the disk makes no difference. The 'resistance' you speak of is still there because the magnetic field doesn't spin with the magnet. This is with the thought the pole-to-pole axis of the magnet is the same as the shaft for the disk.

2. The other is something about different observer frames and perspectives. It is long winded and difficult to believe but is usually voiced by classical physics types. Hopefully one of them will clarify.

Good Luck!

[Mr.Entropy]

if you take 2 flat copper disks and attatch magnets to them and spin them they generate electricity per faradays invention. what is the resistance generated?

Let's say your generator is configured to push electrons out of the outer edge of the disk.  As the disk spins, the atoms in the disk drag the electrons along with them.  We can consider the velocity of an electron in the disk as the sum of two orthogonal components:

1) The tangential velocity component that follows the disk in its rotation.  In the applied magnetic field, this component produces a Lorentz force that pushes the electron radially toward the edge of the disk.  The sum of these forces is the voltage that your generator produces.  They are proportional to the rotational speed, so the voltage is proportional to the disk RPM.

2) A radial velocity component, as the electron moves toward the edge of the disk.  In the applied magnetic field, this component produces a Lorentz force that pushes against the rotation of the disk.  The sum of these forces is the back-torque you feel when you rotate the disk.   Since sum of the radial electron velocities is proportional to the current through your generator, this back-torque is proportional to current as well.

Now, the since power = torque * RPM, the power required to rotate the disk (ignoring friction), is the RPM multiplied by the back-torque produced by the radial component of electron velocities (2).  But RPM is exactly proportional to the generator voltage, and this back-torque is exactly proportional to the generator current, so torque * RPM = VI, i.e., the mechanical power in is the same as the electrical power out.

Cheers,

Mr. Entropy

[sparks]

   I support BEP's answer #1.  There is this fundamental force in the universe that is trying to become equalized.  The permanent magnet's magnetic field arises from the reaction of this force with the quontum configuration of the substances comprising the magnet.  In other words when you move that magnet from point a to point b you aren't moving the magnetism.  You are just going to a different spot in the universe where the fundamental force I call dispersion force reacts with the magnet atoms the same way it did at point a.

[sm0ky2]

Found something kinda fun


https://youtu.be/1m2r8fh8JMA