This weeks quiz question

[Al_The_Man]

What makes the motor run?
http://www.metacafe.com/watch/971400/unexplained_phenomenon_simplest_electric_motor/Al.

[SORCHEROR]

thats easy,the wire acts like a winding,the magnet creates the field and the battery supplies the electricity,you dont have a shaft like a real motor,a normal motor works by charging a wire wrapped on an armature with a magnetic field around it on the outside
when a current is applied the armature,or winding become an electro magnet which will be pushed to move by the permanet magnets feild

[Al_The_Man]

BUT that does not explain how two steady state magnetic fields causes one to revolve without apparent commutation.
A DC motor is normally commutated, mechanically or electronically, how is it achieved in this one?
Al.

[MrWild]

I can't hear the announcer due to deafness, but i can readily see the motor is commutated. The top hook is the positive and the negative is through the magnet/battery interface. The way the motor works is how a field is generated in a wire. What's that physics right hand with the thumb up for current flow direction versus the generated magnetic field in the wire rule?.

The field may be the same strength radially around the wire, but this field is directed towards the center and on the outsde. This coincides with the magnets field and gives a push due to the lopsided nature of the wires magnetic field. I also think the field gives the wire a push in the upwards direction which unloads the weight of the wire somewhat.

The field generated by the wire is also lopsided. More field funnels through the center than the outside. Because of the helix of the wire, spin is induced. I doubt this will work without the helix.

Pretty elegant.

[Al_The_Man]

Originally Posted by MrWild , but i can readily see the motor is commutated. The top hook is the positive and the negative is through the magnet/battery interface.

Technically I don't think that classes as commutation as current or polarity is not changing because of the connection, it is just a means of termination.
Somehow the vector angle has to be maintained between the two magnetic fields in order for motion to be sustained.
Al.

[Madclicker]

Simple. The keywords are "lightly touching" and "properly tuned". The base of the magnet and the top of the battery are the commutator contacts and the current is just switched on and off. Current and/or polarity doesn't have to change direction to spin something. Just switching it on and off is enough, especially if you can hit the natural frequency of the system.

[Madclicker]

Originally Posted by Madclicker Simple. The keywords are "lightly touching" and "properly tuned". The base of the magnet and the top of the battery are the commutator contacts and the current is just switched on and off. Current and/or polarity doesn't have to change direction to spin something. Just switching it on and off is enough, especially if you can hit the natural frequency of the system.

After thinking about this without Friday night beers, I realize I was way off in the weeds. This contraption works by simple EMF forces. The current in the wire creates an EMF that works against the EMF of the perm magnet creating a small force. The Lorentz effect or force, if I remember junior emf physics correctly.

The key to making this work is the orientation of the copper wire to the perm magnet. Everyone remembers the right hand rule?

[HuFlungDung]

Cool

But, I think the thing is inefficient! The coil rubs against the battery accidentally, otherwise under the prescence of a constant force, the thing would accelerate nonstop, rise up off the table and disappear into outer space forever

[Al_The_Man]

Originally Posted by Madclicker the current in the wire creates an EMF that works against the EMF of the perm magnet creating a small force. The Lorentz effect or force, if I remember junior emf physics correctly.

This does not appear to explain how the magnetic vector is maintained to provide motion if both forces are uniform and constant in polarity?

[Al_The_Man]

Here's the Drywall screw version!!
http://www.metacafe.com/watch/479771...lectric_motor/

[Madclicker]

Here's one sculpted into a dragonfly:

http://www.youtube.com/watch?v=FRkj53QTCYE

http://www.youtube.com/watch?v=FRkj53QTCYE

Some people have too much free time.

Here's a wiki entry for these things:

http://en.wikipedia.org/wiki/Homopolar_motor

And another video that shows more clearly how the EMF vectors interact:

http://www.youtube.com/watch?v=w2f6RD1hT6Q

http://www.youtube.com/watch?v=w2f6RD1hT6Q

[Al_The_Man]

So we have a HomoPolar motor, (not that there is anything wrong with that)!!.
BTW The lorentz referred to is not to be confused with LORENZ'S LAW OF MECHANICAL REPAIR- After your hands become coated with grease, your nose will begin to itch.