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Magnets and electricity

  1. Sep 23, 2005 #1
    I know that if you put a magnet in a coil of wire and turn it you can generate electricity, but a friend told me the more coil you use to take more electric you try to make the harder the magnet is to run, the same if you reverse it, even if you turn the coil. Why?
     
  2. jcsd
  3. Sep 23, 2005 #2

    russ_watters

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    Staff: Mentor

    The mechanical energy is converted to electrical energy, which in this case, produces electromagnetism (ehh - induction) in the coil. More coil, means more electromagnetism, so more output produced and more input required.
     
  4. Sep 23, 2005 #3
    Changing magnetic fields produce a current, and currents produce magnetic fields. When you move the magnet you are inducing a current in the coils of the wire. Because there are now currents in the wire, they produce a magnetic field. The magnetic field produced by the currents is oriented such that it resists any further movement of the magnet.
     
  5. Sep 24, 2005 #4
    can a magnet be fullydrained of its magnetic power?
     
  6. Sep 24, 2005 #5

    russ_watters

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    While some types of magnets can lose (or gain) magnetism, using a magnet in a motor or generator does not "drain" a magnet in the way you are asking.
     
  7. Sep 24, 2005 #6
    Magnets may lose their magnetic energy, like elements decay. But as they are really big items in comparison to their tasks - they will last a very long time.

    I believe if you wanted to "burn out" a magnet you could with suffient electrical current flowing through it instead of around it.
     
  8. Sep 24, 2005 #7
    if you put a magnet on a stove it no longer acts like a magnet and becomes a normal piece of metal
     
    Last edited: Sep 24, 2005
  9. Sep 24, 2005 #8

    Mk

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    Works with your computer too!
     
  10. Sep 24, 2005 #9
    lol and will amazingly work on living organisms too! :eek:
     
  11. Sep 25, 2005 #10
    When the magnets spin in a generator to cause the wire in the surrounding coils to charge up, exactly what is the energy? Older books describe the function by claiming Electrons actually move from one length of wire to another.

    But forcing electrons away from their respective atomic nucleus requires enormous energy input. Copper requires alot of energy to remove it's outer electrons since it is a relatively small atom and it's nucleus is still quite close to it's valence electrons.

    In solid materials there usually exist a valance band which is an energy region where the states are filled or partially filled by valence electrons. The conduction band is defined to be the lowest unfilled energy band. So materials can be characterized by their band structure. An insulator has the valence and conduction band well separated. A semiconductor has the valence band close to the conduction band - separated by about a 1 eV gap. Conductors on the other hand have the conduction and valence bands overlapping. But they will often still function with better/worse properties with respect to temperature influence.

    The interesting property of a semiconductor is that thermally excited electrons can move from the valence band to the conduction band and conduct current. Silicon and germanium have thermally excited electrons at room temperature and hence their common use in diodes and transistors.

    So this leads us back to valence energy states, what exactly is the energy, what is it composed of, and what dictates it's strength. As this energy state is increased in an electric current {or magnetic fields} and is induced to travel from one atom to another because Copper prefers to remain Copper and not become Nickel.

    It is a Polar molecule which directs the conditions to provide for conduction of this energy. I think it was refered to as Quarks which are the specific energy, but I'm not certain that is true or even the right answer still today.

    Thanks
     
  12. Sep 25, 2005 #11

    russ_watters

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    First:
    Nothing about electricity implies that copper would become nickel. Electricity has to do with the motion of electrons, and its protons that determine what element something is.

    The thing you need to understand about transferring electrical energy is that metallic bonding makes, essentially, a "sea of electrons" that can relatively freely move through a piece of metal. There is no chemical reaction going on when electricity moves through a wire, as specific atoms don't permanently gain or lose electrons.
     
  13. Sep 26, 2005 #12
    I don't see it that way. The valence electrons can be shared or given to other atoms. but only with the Cu atom nearby to take one back if a better donor comes up.

    The energy potential increases as you go down the table. Gold is a better conductor as it's valence electrons are even further from the nucleus. Yet copper 3+ would be radioactive, which you would say doesn't occur as the electron transfer is continuous. Cu only has 2 stable isotopes and I think free electrons would increase energy transfer potential, but that energy isn't electrons. Electrons {valence or otherwise} would merely jump to the next order of potential in valence shell until the energy is dissipated to an adjoining atom or molecule.
    A sea of electrons would be Plasma like. Something like a Magnetic field without a magnet. Not stable and not controllable without a strong magnetic field.

    Quantum number is the order elements prefer, breaking those rules doesn't mean that electrons are just leaving atoms with only tiny levels of current flowing. The Kinetic energy of the molecule {or atom} just increases, then the Potential goes up as well with amperes.

    I think it's unfair to teach electrons moving in conditions that aren't sufficient to cause it Chemically. They will only learn it doesn't happen that way later on.

    http://www.chemistrycoach.com/quantum.htm
     
  14. Sep 26, 2005 #13
    What I'm saying is, if electron flow were all that was going on superconductive wire would be made of radioactive elements. Simple. But that would require magnetic shielding for insulation. And magnetic fields are not condusive to current conduction. A self defeating theory before they even begin to do their job.

    A superconductive wire is composed of either metal or an oxide. Production of a strong magnetic field is the desired task of these wires. Yet in accomplishing this task they generally defeat their advantages too.
    http://www.chuden.co.jp/english/corporation/press/pre2000/pre0711.html

    Radioactive wires have been made and used. Heat is the prime concern with them and I suppose they oxidize materials nearby quickly.

    Electrical wire is like millions of small batteries end to end. They are weak batteries and don't transfer much power - until induced to do so by a magnetic field generator pushing Potential energy through interaction with elemental electron clouds.

    Superconductive wire is like millions of capacitors connected to each other in comparison, the charge barely needs a nudge to flow energy.
     
  15. Sep 27, 2005 #14

    russ_watters

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    Deckers, you are misinformed. Far short of just being wrong, much of what you are saying doesn't even make sense. You are using words that you clearly do not understand. It's a word-salad.

    We do not entertain such nonsensical discussions here. I highly recommend you learn some real physics.
     
  16. Sep 27, 2005 #15

    Nonsensical notions? Like a sea of electrons?

    You should have paid attention in Chemistry class past the first year.
     
  17. Sep 27, 2005 #16

    Doc Al

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    Perhaps you should review that first year class one more time. The question is clearly about electron flow in wires; your musings about radioactivity are meaningless.
     
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