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Physics Question: Magnets
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Magnetism is at the heart of modern technology. Moving permanent magnets through coils of wire (or vice versa) is the primary, and most efficient method of converting mechanical energy into electricity, and electrical energy into mechanical energy. In this situation, the magnetic field forces electrons to flow, and moving electrons create their own field that attracts/repels the poles of a magnet to produce movement.
Here's the questions: Does the field of a "permanent" magnet deteriorate over time? When magnetic attraction makes something move, how is the Law of Conservation of Energy observed? Where does the energy to move those things come from and does it "run out" or "get used up"? And finally, how "permanent" are permanent magnets?
I can understand and explain the quantum effects that allow transistors to work, but I can't yet get a grip on the forces behind how magnets work... Please enlighten me.
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Glenn -----OTR/L, MOT, Tx
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"…I contend that we are both atheists. I just believe in one fewer god than
you do. When you understand why you dismiss all the other possible gods,
you will understand why I dismiss yours." - Stephen F. Roberts
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Good one. I hadn't found anything like that forum. The discussion did, however, ignore the situation regarding magnetic pull making something move toward a permanent magnet. Does the paper clip move to the bar magnet using some of the energy used to magnetize the bar magnet? If not, where did that energy come from?
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Glenn -----OTR/L, MOT, Tx
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Blandine Bureau 1940 - 2011
Missed 2012 by 3 days, RIP Grandma :-(
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Originally Posted by ghporter
Does the paper clip move to the bar magnet using some of the energy used to magnetize the bar magnet? If not, where did that energy come from?
No it doesn't use energy used to make the magnet. Energy is conserved because the same energy that was used to pull the paper clip to the magnet is required to separate them. Think of this as converting potential energy to kinetic energy. Think of this as the molecular force that it is. Lets consider chemical reaction forces. Imagine you have a room that you have filled with 1 part oxygen and 1 part hydrogen. You only need one little spark and the whole room goes boom (binding the atoms to create water); does that mean you created energy from nothing? Or from just one little spark? Of course not. The forces of the charged particles had potential energy and when a spark occurred it caused the opposite charges to attract in a way that caused a reaction; a release of energy; but the same amount of energy is required to separate the hydrogen and oxygen again. We don't say that the charge of oxygen or hydrogen is free energy.
edit: for the record magnetism is a force, and energy is force x distance or something right?
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(
Last edited by ghporter; Dec 13, 2011 at 08:02 AM.
)
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Originally Posted by el chupacabra
No it doesn't use energy used to make the magnet. Energy is conserved because the same energy that was used to pull the paper clip to the magnet is required to separate them. Think of this as converting potential energy to kinetic energy. Think of this as the molecular force that it is. Lets consider chemical reaction forces. Imagine you have a room that you have filled with 1 part oxygen and 1 part hydrogen. You only need one little spark and the whole room goes boom (binding the atoms to create water); does that mean you created energy from nothing? Or from just one little spark? Of course not. The forces of the charged particles had potential energy and when a spark occurred it caused the opposite charges to attract in a way that caused a reaction; a release of energy; but the same amount of energy is required to separate the hydrogen and oxygen again. We don't say that the charge of oxygen or hydrogen is free energy.
edit: for the record magnetism is a force, and energy is force x distance or something right?
Thanks! Both for the reminder about energy versus force and for the simple illustration of "energy used" to attract the paper clip. Much clearer now.
With so many technical levels involved, it's sometimes easy to trip over one of them and get muddled.
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Glenn -----OTR/L, MOT, Tx
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Originally Posted by FireWire
WTF?
That was funny.
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Maybe funny-ish, but quite distracting. And since I left the link, all are welcome to check it out. (I think intentionally creepier-than-usual clowns are a distraction to begin with...)
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Glenn -----OTR/L, MOT, Tx
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Originally Posted by ghporter
Maybe funny-ish, but quite distracting. And since I left the link, all are welcome to check it out. (I think intentionally creepier-than-usual clowns are a distraction to begin with...)
But you left Brien's photo up?
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Creepy versus creepy with vulgar wording... I left that one because it didn't seem quite as distracting. I probably would have done something about that one too if I'd thought more about it, but the vulgarity is what really caught my eye.
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Glenn -----OTR/L, MOT, Tx
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Is this one better?
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Originally Posted by Brien
I love this meme.
Too bad it illustrates that NN is starting to become out of touch with the internet.
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Originally Posted by Dork.
Is this one better?
Is that John Inman?
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What, me worry?
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Originally Posted by The Final Dakar
I love this meme.
Too bad it illustrates that NN is starting to become out of touch with the internet.
I'm sorry that removing an "F-bomb" from what had been a technical discussion makes it seem like I'm "out of touch" with anything...
I concur with the superiority of the newly placed image.
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Glenn -----OTR/L, MOT, Tx
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