# Magnetic Electricity Generation

Discussion in 'General Science & Technology' started by DJ Erock, Jul 10, 2006.

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1. ### DJ ErockResident SkepticRegistered Senior Member

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What if you set up a turbine that is powered by magnets. I've seen magnet powered trains, I think in Disneyland or something, that were run on the resistance of magnets to each other. Using this idea, you could mount magnets on a turbine, and then surround it with magnets that push against them. If they are aligned at the right angles, they should spin the turbine that would generate electricity. Would this work?

3. ### kevinalmRegistered Senior Member

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No. This idea crops up from time to time. It won't work. The pat answer is that it violates the law of conservation of energy, (which it does). I know you probably won't find that satisfying so I'll try something a little more to the point.

Take two permanent magnets. Move them around each other, turn them this way and that, and so forth. Sometimes they attract, sometimes repell. Sometimes you will do work on the magnets, sometimes they will do work on you. The point of this excersize is that the laws of electromagnetism mandate that net work done by the magnets on you is at best zero for any repeatable "loop" of position and orientation. It can be less than zero (you do net work on the magnets) if for example you move the magnets near something conductive inducing eddy currents and generating heat. But the best you can do is zero.

So how does an electric motor work then? Well using an electromagnet in the motor you can creat nonzero "loops". (By varying the strenth of the electromagnet over time.) Guess what, the minimum electrical energy required to do this is equal to the "nonzeroness" of the loops. Kinda neat how energy is conserved, huh?

5. ### leopoldValued Senior Member

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i'll agree with kevin. and add the following.

electric motors work because of:
1. a rotating feild
2. by the use of a commutator

1. is employed in ac motors. by proper phasing the feild can be made to push the armature around

2. is used in dc motors and switches the feild at the right time to acheive the same effect as 1.

if you could replace one set of magnets, either the stator or the armature, with electromagnets then the turbine idea would work. but of course you would need to apply power to the electromagnets in the right phase.

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8. ### leopoldValued Senior Member

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you do realize that dj is describing a perpetual motion machine don't you?

9. ### TheoryofrelativityBannedBanned

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http://www.re-energy.ca/pdf/cp2.pdf

her's a DIY page on how to build your own hydroelectric generator.
It creates a current of electricity in a coil of wire using moving magnets

10. ### leopoldValued Senior Member

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he is describing a setup that has pm magnets for both armature and stator.

the link you gave is the good old hydro-electric generator that is used at dam power stations

11. ### TheoryofrelativityBannedBanned

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ohhhh, trying to reinvent the wheel

anyone here got a Levitron?

12. ### TheoryofrelativityBannedBanned

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http://www.amasci.com/maglev/levtr1.html

"IT'S AN EXTRAORDINARY SIGHT -- a magnetic top spinning, bobbing and weaving in space for two minutes or longer. It remains levitated two or three inches above a larger base magnet. The top is not touching any other object, and no strings, electricity or other devices are used.

Levitation is one of mankind's oldest dreams, and it has now been achieved using just a few dollars' worth of ordinary permanent magnets and some pieces of plastic.

Anyone with even a casual interest in physics has to be amazed. For more than 150 years, such levitation was "known" to be impossible."

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14. ### DJ ErockResident SkepticRegistered Senior Member

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So the refute of this idea is in that you wouldn't be able to postion the magnets at angles that would keep the wheel spinning?

15. ### leopoldValued Senior Member

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don't forget you also stipulated that electricity is to be extracted from this setup.

16. ### DJ ErockResident SkepticRegistered Senior Member

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right, but the spinning of the wheel is the key to generating electricity, unless i'm mistaken.

17. ### leopoldValued Senior Member

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you are correct. the spinning wheel is the key.
but you intend to extract energy from this device. where does this energy come from? if it comes from the device itself then you are describing a perpetual motion machine.

18. ### DJ ErockResident SkepticRegistered Senior Member

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I don't know exactly how electricity is generated, but I'm thinking that the wheel being spun by the magnets is connected to like a drive shaft or something that would connect to whatever it is you spin to make electric

19. ### leopoldValued Senior Member

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electricity can be generated in at least two ways
1. chemical (batteries)
2. a coil of wire moving in a magnetic feild

number 2 is our concern

you need to understand a few things about coils of wire.
when a coil of wire move through a magnetic feild the feild generates a current in the wire when a load is placed across the ends.
as soon as the current starts to flow it generates a magnetic feild
this second feild generates what is called a 'back emf'
this back emf will prevent the setup you describe from working.
it also explains why a generator is harder to turn the more current that is drawn from it.

20. ### DJ ErockResident SkepticRegistered Senior Member

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So yeah, you connect a shaft from the spinning wheel that the stationary magnets create to an electromagnetic generator, or whatever you call it. If you need to seperate them so that they don't interfere with each other, then it will be a bigger setup than I planned, but wouldn't this still work?

21. ### DJ ErockResident SkepticRegistered Senior Member

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And how does a coal burning plant produce electricity?

22. ### leopoldValued Senior Member

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no. electricity is energy. in order to extract energy from your setup the back emf will prevent it unless energy from outside the system is applied.

how coal is used to produce energy.
one word, steam
coal is used to heat water to the boiling point and beyond.
the steam that is produced is channeled through the turbine blades to rotate the generator.

23. ### DJ ErockResident SkepticRegistered Senior Member

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but if you seperate the two magnetic fields, by way of a huge lead wall, or whatever you have to do, then how is the wheel powered by magnets any different than steam in turning the generator?