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Can I produce electricity by using permanent magnets with no moving parts?

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Ksree
#1
May21-06, 03:28 PM
P: 8
Is it possible to produce electricity by using permanent magnets with no moving parts?
I believe that is possible. Because AC current produced by moving armature or copper wire or some other metal in magnetic field. Then without moving wire it should produce DC or some kind of electron flow.
Am I missing some thing?

Please note that I do not have good knowledge in Physics or electrical engineering. If my question sounds so stupid or dumb, please excuse me.
I tried to get some answer to my question by searching web and I posted on some other forums. But I did not get satisfactory or justified answers.

KSREE
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Mike Phan
#2
May21-06, 06:29 PM
P: 67
If you say that "AC current produced by moving armature or copper wire or some other metal in magnetic field", why don't you think that without that moving, no AC produced, but you think without that moving a DC would be produced?

I think that the AC produced because the moving in different angles. For me, it is impossible to electricity without moving parts because "no give, never get" (smile)
Cliff_J
#3
May21-06, 06:34 PM
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The AC you refer to is produced by a rotating magnet or coil of wire, and as it rotates it goes North-South-North-South and that creates the AC. A DC motor (that can also be a generator) uses brushes on a commutator that switches the coils so that the north is always on one wire and same for the south. An alternator takes the AC output and uses diodes (one-way electrical valves) to make DC.

Basically, you need to cut magnetic field lines (maybe you remember the lines iron filings made on a bar magnet in school if you did the experiment) to induce an electrical current in a wire, and that's usually done with physical movement like rotation.

A transformer uses no moving parts, but only works with AC. It has two coils and a iron core to concentrate the magnetic flux, and the AC that is fed into the one coil creates a varying magnetic field that is picked up by the other. But if you fed it DC, you get nothing from the second coil after the initial pulse.

So you basically need physical movement or a changing magnetic field. And since all the physical movement does is basically create a changing magnetic field, that is really the key for an magnetic-to-electrical conversion. A permanent magnet doesn't have a changing magnetic field - unless you can wait years for it to dimish, but what good is that?

On top of that, if you had a generator that was producing say 12V and 100A of current, which is 1200W of power, you would need more power than that to spin the generator, say 1400W, because the energy needs to come from somewhere whether its a windmill or a water turbine or a gasoline motor. But something needs to put in the mechanical power before the generator can convert it to electrical power (and some lost as heat).

Gokul43201
#4
May23-06, 02:16 PM
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Can I produce electricity by using permanent magnets with no moving parts?

Quote Quote by Ksree
Is it possible to produce electricity by using permanent magnets with no moving parts?
I believe that is possible. Because AC current produced by moving armature or copper wire or some other metal in magnetic field. Then without moving wire it should produce DC or some kind of electron flow.
Am I missing some thing?
Yes, you are. The current produced is proportional to the rate of change of flux through the current loop.

If the flux changes sinusoidally, so will the current, since the derivative of sin(wt) is just w*cos(wt) = w*sin(wt-pi/2). If the flux does not change (ie: is constant), there will be no current, sice the derivative of a constnt number is zero.

This does not mean it's impossible to produce a current from permanent magnets without motion. I can think of one way to achieve that, but I don't see it being particularly useful.
Suerbatica
#5
May24-06, 01:12 AM
P: 10
I just spent 40 minutes writing the most accurate response in history... only to be logged out by the website and my response trashed.

Suerbatica
NoTime
#6
May24-06, 02:10 AM
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Quote Quote by Gokul43201
This does not mean it's impossible to produce a current from permanent magnets without motion. I can think of one way to achieve that, but I don't see it being particularly useful.
Hall effect?
I thought that required a perpendicular bias current.
Am I missing something or are you just feeling obscure today?
pallidin
#7
May24-06, 03:37 PM
P: 2,292
Quote Quote by NoTime
Hall effect?
I thought that required a perpendicular bias current.
Am I missing something or are you just feeling obscure today?
Wondering the same thing. Perhaps Gokul could elaborate.
Gokul43201
#8
May24-06, 08:02 PM
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Quote Quote by NoTime
Hall effect?
I thought that required a perpendicular bias current.
Yes it does - that wasn't what I was thinking of though. Nevertheless, it does satisfy the OP's quest of an induced current without moving stuff.
Am I missing something or are you just feeling obscure today?
A little bit of both perhaps. My idea was way more harebrained. You heat/cool a magnet across its Curie temperature to change the field produced by it !
NoTime
#9
May25-06, 12:55 AM
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Quote Quote by Gokul43201
A little bit of both perhaps. My idea was way more harebrained. You heat/cool a magnet across its Curie temperature to change the field produced by it !
That would work.
Cliff_J
#10
May25-06, 08:10 AM
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Nice, hadn't thought about actually using the Curie to have a desired effect!

Too bad the thermal mass and energy required make it very impractical, but within the realm of possible.
nik282000
#11
May25-06, 10:48 AM
P: 6
Once you heat it past the Curie temperature it losed its ability to hold a madnetic field and AFAIK it loses its maknetization completely so you would really only beable to do it once.
Gokul43201
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May25-06, 11:10 AM
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Quote Quote by nik282000
Once you heat it past the Curie temperature it losed its ability to hold a madnetic field and AFAIK it loses its maknetization completely so you would really only beable to do it once.
That's not entirely correct. If you cool down below the Curie point, the material will go ferromagnetic once more. Only, it will not likely have a net magnetization, as the domains will cancel each other. But I've got a kluge for that too. You use two magnets : (i) a field source, and (ii) the temperature controlled magnet.

When the second magnet is lowered below the Curie temperature, it gets reoriented by the field of the source magnet.

Anyway, this is an inefficient and impractical way to generate AC, as I mentioned earlier.
ganeshram
#13
May30-06, 08:42 PM
P: 1
what must be the size of the magnet to produce 130 volts
Averagesupernova
#14
May30-06, 10:49 PM
P: 2,537
Quote Quote by nik282000
Once you heat it past the Curie temperature it losed its ability to hold a madnetic field and AFAIK it loses its maknetization completely so you would really only beable to do it once.
Not even close. Some temperature controlled soldering irons are controlled this way. The back end of the tip is magnetic and when heated past a certain point loses its magnetism which opens a reed switch which turns off the heating element. See where this is going?
pallidin
#15
May31-06, 07:32 PM
P: 2,292
Perhaps not very effecient, but an interesting concept!! Congrats Gokul, especially with respect to using a re-normalization magnet. Nice.
Cliff_J
#16
Jun2-06, 04:18 PM
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Quote Quote by ganeshram
what must be the size of the magnet to produce 130 volts
There are many different parameters that would need to be factored in to determine this. If your target voltage was 130V, then you likely have a desired power output as well so you'd want to factor that in to the calculations as well.

But the voltage produced would roughly be based on:
-The strength of the magnetic field (strength of magnet minus the distance away from it)
-The permeability of the core the wire is wound on
-The number of turns of wire
-The speed at which the field lines are being cut (like RPM)

So even a small weak magnet could be put into a situation where it produces 130V with little current/power, or a very large and strong magnet would make only a few volts because of how it was utilized.
Dael
#17
Jan21-09, 08:54 PM
P: 1
The expression “A changing magnetic field causes a corresponding change in an electric field” will lead some to confusion. A magnetic field of any strength is a result of microcosmic electric fields aligned north and south within a magnet. The magnetic field is the result of these constant, unchanging electric fields. If a magnetic field is going to do anything it will only attract, repel or orientate similar microcosmic particles. This action works to completion and comes to an end. It could be said that some energy absorbed by microcosmic electric fields external to the magnet might take some of the energy of the electric fields within the magnet or at least some of the energy within the magnetic field itself until equilibrium is reached. After this point is reached no change in any electric field is made—the magnetic field is constant. A changing magnetic field really means a rotating or oscillating magnetic field, such as expressed above as magnetic lines must be cut or change in direction, must be mechanically applied.
This leads one to consider that a changing electric field produces a changing magnetic field. If we say that a constant or alternating electric field causes a constant or alternating magnetic field, we would be more correct. This requires mechanical input or the result of moving charges within a DC battery. But a constant magnetic field does not produce a constant electric field because it is already the result of an infinite number of constant microcosmic electric fields. The use of the word “changing” by writers causes some to think of the word “moving.” This is the problem with the original question.
Airbag79
#18
Jan21-09, 10:25 PM
P: 7
Quote Quote by NoTime View Post
Hall effect?
I thought that required a perpendicular bias current.
Am I missing something or are you just feeling obscure today?
Hall effect is the asymetrical charge distribution of a electrons on conducting medium when orientated perpendicular to a magnetic field. The asymetric charge distribution creates a quantitative voltage drop on the conductor. Irrespective to the OP's inquiry.


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