Friction with a Magnetic Bearing System?

Thesnake22

One question that I have been thinking about for a while is if you were to use magnetic bearings (no physical friction) for a type of motor and put energy into it by spinning it and slow it down with another magnet, where does the mechanical energy go? If there is no physical contact with the bearing will it produce heat because of the magnetic friction? or Will the energy be completely destroyed?

CWatters

What do you mean by "slow it down with another magnet" ?

"Slow" implies a load of some sort and that's your answer.

Thesnake22

"By slowing it down with another magnet," I mean that the magnet is used as a form of friction and prevents the motor for rotating after the work is applied to it.

Drakkith

Magnets don't work by friction. Instead like poles repel each other. If you don't have enough momentum or velocity to overcome this repulsion the motor would simply come to a stop and then be accelerated the other way before coming to a stop again as it approached the magnet once more. In a perfect system with no losses it would simply oscillate back and forth.

If instead you had enough velocity to overcome the repulsion, the motor would slow down as one of its poles approached the magnet and then accelerate back up to speed once it passed the magnet. No energy loss.

However, we don't have perfect systems in real life. You will lose energy through friction with the air and with the flexing of the magnet and motor.

CWatters

I suppose a magnet could slow the motor by causing eddy currents. Bit like a dynamo with the output shorted. In which case the energy would go into heating the motor.

Thesnake22

I'm sorry, I forgot to mention that the motor is attached to another system (which is a magnetic rotating shaft). You first transfer the energy from the motor to the rotoring shaft then disconnect the motor, so that the shaft is running off momentum. Then have the magnets attract one another. Should the attraction of the magnets slow the staft to a stop?

Thesnake22

Anybody?