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View Full Version : OT-ish; nice magnet trick



Ian B
11-20-2007, 02:13 PM
Saw this, haven't tried it yet:

http://www.supermagnete.de/eng/project1

Ian

dp
11-20-2007, 02:28 PM
The homopolar motor: http://en.wikipedia.org/wiki/Homopolar_motor

Interesting principles at work.

ZINOM
11-21-2007, 12:11 AM
If you read the text near the top it seems a little odd that they appear to be so amazed with the discovery....they sell MAGNETS don't they??

I like things like the homopolar motors and stuff that easily shows kids direct applications of science.

John

Fasttrack
11-21-2007, 03:32 AM
If you read the text near the top it seems a little odd that they appear to be so amazed with the discovery....they sell MAGNETS don't they??

I like things like the homopolar motors and stuff that easily shows kids direct applications of science.

John


me too - i love physics and i love being able to show it off when i ever i get the chance. Especially demonstrations that require some machining like the gyroscope i made last year that shows precession and the effects of gravity on the precession of the gyro. Thanks everyone who had input on that project, btw!

Not to steal the thread, but i'd like to hear other suggestions for projects for a HSM that could be used to teach physics.

Weston Bye
11-21-2007, 12:22 PM
There is something similar from one of the Boy Mechanic books:

Mill/machine/rout a circular moat in the surface of a board, Place a magnet, poles vertical (top & bottom)on the island in the center of the moat. suspend a wire on a metal hook with a loop or eye at top, centered over the magnet and bottom end in moat. Fill moat with mercury, :eek: :eek: :eek: attach battery to mercury and hook suspending wire. The wire will rotate around the magnet.

dalesvp
11-21-2007, 03:23 PM
Here is an interesting experiment that has befuddled many an electrical engineer.

http://www.svpvril.com/armature/armature.html

JS
11-21-2007, 08:05 PM
There was a group of people in Australia ? I believe who used this method to make a generator applied 12 volts to maintain the field and supposedly made 14 k of power .

Paul Alciatore
11-22-2007, 01:26 AM
Perhaps they were surprised or amazed, but no physicist would be. The current is passing radially through the magnet and setting up it's own magnetic field. A magnet within the magnet, so to speak. This field interacts with the permanent field and causes the rotation.

There is an early, elemental generator that consisted of a conducting disc that was rotated on a shaft. There was a magnet that had opposite poles above and below the disc on one side of the shaft and wires were connected to the shaft and to a brush on the outer edge of the disc in the same direction as the magnetic field is from the axis. When it rotates, a DC current is generated.

It is essentially one wire winding that is continously replaced with fresh conductor via the rotation of the disc. As the disc (wire) passes through the magnetic field, a current is generated. Not very efficient as it is effectively only a single winding and real generators, even low Voltage ones on vehicles, have many windings to obtain a higher, useful Voltage.

Many motors can be used as generators and many generators can be used as motors: reciporical effect. Motion in a magnetic field generates electrical current and current in a magnetic field generates torque or motion. This magnet motor is just the reverse of that simple generator. Nice parlor trick, but not necessairly very useful. But perhaps with the super magnets something useful could be made.