Question about magnets

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A 9 yr old had a question I couldn't answer. Where do magnets get their power? Why doesn't it run out?
Thanks FINOH #29718 Finoh #28437 FiNOH #27447 I love spacefed.
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FiNOH wrote:

They get their "power" from different things. In the case of natural magnets they get their power from the spinning of the earth.
Power is not a good term to use, because it is likely to be confused with energy. Their power is a magnetic alignment that creates a static field when may well extend well beyond the magnet. When the field is static, no energy is used.
Moving the field takes energy and the movement of the filed creates an opposing energy. That is why moving a wire through a magnetic field will move electrons (electricity) in the wire.
OK guys, that is overly simplified, but that is the idea.
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Joseph Meehan wrote:

Not really. It's from the alignment of the individual minute magnetic fields of the orbiting electrons in the individual atoms. A fairly nice discussion is at
http://www.coolmagnetman.com/maghow.htm
In a random chunk of ferromagnetic material, the microscopic magnetic domains have a random orientation yielding very little or no net magnetic force. Introduction of an external field can cause the alignment of these domains. Once removed, in some materials (termed "hard" magnet materials) a significant fraction of these domains will retain this alignment, thus creating a permanent magnet.
As you allude to, there is also, of course, electromagnetism which is induced by a varying external field.
Magnetism is a fascinating area of exploration for young (and old, too, for that matter)...
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dpb wrote:

When heat treating high carbon tool steel to harden and temper it, you can tell when the proper temperature has been reached by holding a magnet to it. At that point, called the Curie point, the domains fall apart and the magnet no longer sticks.
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Joseph Meehan wrote:

Just last week I learned a neat simple demo you can do with high energy magnets.
I used a 1/2" diameter by 1/2" long magnet, but it could as well have been two or three thinner 1/2" diameter magnets stuck together.
When dropped into an upright foot long length of 1/2" copper water pipe the magnet, which fits quite loosely inside the pipe, takes several seconds to decend through that length of pipe.
What's happening is that the moving magnet's field induces a current into the copper pipe and that current flowing through the copper creates an opposing magnetic field which wants to keep the magnet where it is, thus slowing its fall.
It's a simplified example of the resistance you can feel with your fingers if you spin the shaft of a small permanent magnet DC motor with and without it's power terminals shorted.
Jeff
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Jeff Wisnia wrote:

Cool! If you force it through, will the pipe get warm?
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CJT wrote:

Yes, but it'd take a pretty sensitive temperature measuring device to measure it. <G>
Jeff
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As said,

You can hold a piece of wire in your hands with an analog volt meter clipped on each end. Pass it through the N & S poles of a magnet fairly rapidly. You'll see the needle jump for a bit.
Why do this? Well, it gets the kids attention. Not as much as tossing a small piece of dry ice in water though. Using water with food coloring in it then drinking the water afterwards makes the tykes seriously wonder about you.
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Al Bundy wrote:

I always thought magnets got their power from refrigerators
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Yea but frigs get it from the TV.
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Shorting the power leads of a motor is sometimes used for quick braking.
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Chris Lewis, Una confibula non set est
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snipped-for-privacy@nortelnetworks.com (Chris Lewis) writes:

or hooking it up to an ultra-capacitor/battery for regenerative breaking. ;)
I believe intentional shorts are called shunts.
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Even though this is not the right place to ask the question, my take is the following.
The alignment of the orbits of the electrons in a "magnet" are such that when introduced to another ferrous object, that object is forced to align its electrons which creates a vector force in a manner equal & opposite to the "magnet's".
A magnet doesn't "have power" - it simply possesses properties that attract ferrous materials to it. Sort of like elemental valencies that complement a full shell in chemistry, but the force is magnetic, not electrostatic. The magnetic "force field" it creates actually is net vector zero, and the attractive force is equal & opposite to whatever is holding the magnet. So to do the work, you need to work.....
It's not a simple explanation for a nine year old whichever way you look at it, in fact some university physics students would have problems explaining it.

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FiNOH wrote:

This should answer: http://science.howstuffworks.com/electromagnet.htm
Better bookmark that place, as apparently you have a 9YO with an inquisitive mind.
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FiNOH wrote:

Apparently you never had magnets as a child and know nothing about magnets, the power does run out. Electro-magnetism is one force, another is gravity. Here is your question, name two other natural forces!
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arrogance and stupidity?
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Larry Wasserman - Baltimore, Maryland - snipped-for-privacy@charm.net
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snipped-for-privacy@fellspt.charm.net wrote:

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George E. Cawthon wrote:

GOODBYE GEORGE!
PLONK
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jJim McLaughlin wrote:

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What an asshole.
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