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Thread: Electromagnet Question

  1. #1 Electromagnet Question 
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    Are electromagnets only activated by electricity or do they actually consume electricity?


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  3. #2  
    Forum Ph.D. william's Avatar
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    Anytime you have resistance, you'll lose energy in the form of thermal energy. So if the electromagnet has resistance (which I believe most if not all do), I suppose you could say that they "consume electricity."

    Cheers,
    william


    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  4. #3  
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    Well, can you, or anyone else, tell me exactly how much energy is lost - or electricity, in watts, would be required to operate an electromagnet?
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  5. #4  
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    Yeah, no problem,

    THere's a long list of things I need to know first...

    Structure of the core (iron,copper, percentage of other elements..)
    Wire thickness and resistivity, ambient temperature, structure of the wire...

    Number of turns, diameter of core, distance between core and winding,
    Mass of the core, thickness of insulation,

    Jesus, the more I think the more I remember it needs!

    AC or DC, IF ac then Applied RMS voltage, frequency, wave shape....

    oh I almost forgot shape of the core and coil, average radii (of several parts)

    Why not just measure the current and voltage and multiply them together to get the power - it's easier.

    By the way solenoids, relays, motors and all other electromagnets are usually constructed from tables of data.

    It's a whole science in itself....

    Why not ask something simple like "How long is a piece of string :wink:
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  6. #5  
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    Ok, thanks.

    The reason i'm wondering is I learned about these electromagnet trains and it gave me an idea for a generator. I thought maybe you could make the 'train-track' simply loop into a circle and in doing so, create the beginnings of a generator. And this generator could possibly generate more electricity than it requires to operate; and therefore power itself while also providing an energy surplus.
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  7. #6  
    pmb
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    Quote Originally Posted by Jonesy
    Ok, thanks.

    The reason i'm wondering is I learned about these electromagnet trains and it gave me an idea for a generator. I thought maybe you could make the 'train-track' simply loop into a circle and in doing so, create the beginnings of a generator. And this generator could possibly generate more electricity than it requires to operate; and therefore power itself while also providing an energy surplus.
    What you're speaking of is a free-energy device. The second law of thermodynamics states that a free-energy device cannot exist (i.e. energy must always be conserved). There is energy lost when the train runs. Part of that energy is disapated by in the heat due to friction of the moving the parts. With all sources of friction removed then the maximum theortical limit for the free-energy which can be produced is zero.

    Best wishes

    Pete
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  8. #7  
    Forum Sophomore Kabooom's Avatar
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    Is there such thing as some form of electricity conduction without any resistance, even in theory? And if you had this 'wire' in an electromagnet would it use any electricity?
    WHAT?!
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  9. #8  
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    Quote Originally Posted by Kabooom
    Is there such thing as some form of electricity conduction without any resistance, even in theory?
    Simple.

    R = E/I.

    So, no.



    E = I * R
    E = I * 0
    E = 0

    Again, no.
    Let me warm up first....don't want to pull a hammy.
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  10. #9  
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    Quote Originally Posted by Kabooom
    Is there such thing as some form of electricity conduction without any resistance, even in theory? And if you had this 'wire' in an electromagnet would it use any electricity?
    The answer to this question is a very definite YES - despite what others may say, look up superconductivity. The problem is the amount of energy required to keep conductors 'super-cooled' - some modern materials do not need to be cooled to absolute 0 to achieve superconductivity.
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  11. #10  
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    Indeed.

    So superconductors can have current with a zero applied voltage?

    Interesting......thanks for the correction.
    Let me warm up first....don't want to pull a hammy.
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  12. #11  
    Forum Sophomore Kabooom's Avatar
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    Ahh, superconductors, I have heard of them but didn't quite know their uses. Now obviously it would take a lot of energy (to remove it, seems ironic) to get the superconductor down to zero resistance, but if you did could you have an electromagnet that used no electricity (not counting the cooling)?
    WHAT?!
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  13. #12 Electromagnetics 
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    i find it interesting that according to maxwell's and heinrich hertz's equations, a time-varying electric field generates a magnetic field and vice versa.

    so according to that statement, if you can pump enough of a magnetic field out of something without the use of electricity, a subsequent electric field would inturn be generated?

    ifso could the new raw electric field be harnessed and recycled back through the magnet creating a stronger electric field and magnetic field?

    and if that is the case would it be a never ending electric and magnetic buildup till the magnetic field was soo strong that it would atrract a gravitational pull on a planetary scale?

    mmm deep thoughts...
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