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Where do electrons come from?

  1. Nov 2, 2008 #1
    I just want to know where the electrons come from when a magnet passes through a copper induction coil. Do the electrons come from the copper coil itself( ultimately breaking down the copper over time), or is the electrons coming from the surrounding environment. If the electrons are coming from the surrounding environment could someone tell me where to find a published scientific experiment that supports that electrons are being "pumped" into the coil by the magnets?

    Why do generators go bad?

    Also, in a solar panel, are the electrons coming from the light energy hitting the material (light energy being absorbed and then given off as electrons), or is the light energy exciting and breaking off the electrons of the solar panel material (ultimately breaking the material down)

    Why do solar panels go bad?

    Thank-you so much. I think this will help me have an understanding of similarities or differences between electromagnetic energy and magnetism and electricity.
  2. jcsd
  3. Nov 2, 2008 #2
    The electrons 'come' from the copper itself. The magnet is just inducing a force which circulates the electrons in the opposite direction of the electric field generated. The copper doesn't have electrons 'used', they are just circulated. So, if you were to constantly move the magnet through the copper forever, charge would still be produced.

    Not too sure what you mean by the second question.

    In a solar panel, the electrons come from the material of the solar panel. They are 'knocked' loose because photons (light) of a certain energy level are able to eject electrons from the material the solar panel is made of. The solar panel is constructed so that these electrons all follow the same direction, and are circulated, creating an electric current.

    Again, you will need to elaborate further for this question. But hope the above helped!
  4. Nov 2, 2008 #3
    Generators typically "go bad" because of mechanical wear and heat. Common failures include insulation breakdown, bearing failure, and commutator/brush damage.
  5. Nov 2, 2008 #4
    Ok, so the magnetic field induces the electrons to circulate in the wire. What happens to the electrons when a load is put in the wire circuit (like a light bulb or an electric motor). Aren't some of those electrons being converted into other forms of energy like electromagnetic energy (light and heat), because doesn't electromagnetic energy also have characteristics of mass. For example, doesn't Einsteins equation E=mc^2 explain that energy (electromagnetic energy) is a form of mass and mass is a form of energy?
  6. Nov 2, 2008 #5


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    No, electrons are not "converted into energy"- no non-nuclear process can convert matter to energy. What happens is that the kinetic and/or potential energy of the electrons is reduced. That is where the energy comes from.
  7. Nov 2, 2008 #6
    What do you mean that the electrons kinetic and potential energy is reduced? Where is the heat or light coming from? In a nuclear reaction isn't mass being converted into energy via fission of an unstable atom?
  8. Nov 2, 2008 #7


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    When water turns a turbine (thus, converting some of its energy into electricity), do you think this is a nuclear reaction where some of the water's mass got converted to energy? When you drop a rock onto the ground, (and thus, letting gravity do work on the rock), did the rock lose mass?

    Many of these are NOT as exotic as you think.

  9. Nov 2, 2008 #8
    Re DDarcade's question?

    Does the light get produced by changing the frequency of surrounding heat?
    Can you light a bulb while it is in liquid nitrogen?
  10. Nov 2, 2008 #9


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    Er... "frequency of surrounding heat"?

    If someone just look into how those EM radiations are produced in a synchrotron center, one would clearly see that all it took is to have those bunches of electrons going round and round in circles AND to make them "wiggle" as they pass through a series of magnets. Voila! You get light/EM radiation! That wiggling is also the basic foundation for free-electron lasers. So all it takes to produce "light" is an accelerating/oscillating set of charges. No "atomic transition" of any kind here, and no "frequency of surrounding heat", whatever that may be.

  11. Nov 2, 2008 #10
    Are these things you speak of doable in a liquid nitrogen cooled environment?
  12. Nov 3, 2008 #11
    In fact the rock may have very well lost mass. When the rock collides with the ground, the collision creates frictional forces. Electromagnetic energy is produced due to the collision. Electromagnetic energy has mass characteristics, and it must come from the mass of either the rock or the ground due to the law of conservation of energy.

    I think we're getting off the subject. So, I'll ask the question again but with some additions.

    Visualize a coil of copper wire that passes through magnets (a generator basically). The copper wire is grounded into the earth, but has a load (a light). When the magnet passes over the coil, do the electrons come from the coil and travel through the circuit to the ground? Thus, making the copper coil lose mass? and disintegrate over time?

  13. Nov 3, 2008 #12

    In a complete circuit as you describe, as the electrons move from the copper coil to ground they are replaced by electrons moving into the coil from ground.

    But, your basic question might be better considered with static electricity.

    Would a positively charged sphere have less mass than one that is neutral? Yes. Would it "disintegrate"? No.

    You might be thinking on the terms of striping the lone electron of a hydrogen atom, which would indeed cause catastrophic structural problems, but this is not the case with higher metals such as copper.
  14. Nov 3, 2008 #13
    Most importantly, consider "free" electrons, responsible for current flow. They are not "bound", thus do not participate in co-valent bonding.
  15. Nov 3, 2008 #14


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    Electromagnetic energy has "mass characteristics"? Really? Other than the binding energy, which is beyond classical E&M, can you show where such "mass characteristics" comes in?

    I think this is basic circuit problem. As palladin has mentioned, you have a closed loop where charges continue to flow in an out at a steady rate. I'm not exactly sure why this is a difficult point to understand.

  16. Nov 3, 2008 #15
    Let's use an analogy to start: think of a hose with water and a pump...if you activate the pump it will move the water in the hose, lets say to a higher level, where it will gain potential energy; hence the ability to do work....but the water will flow only briefy, then it runs out....But if the returning falling water is returned to a bucket, the pump will continue to circulate the water. The higher the water pressure, the more work can be done.

    So to supply any measureable power we need a complete circuit to reuse electrons (water):

    The electric coil is similar...apply an EMF via rotation, or a battery, and some loose electrons may briefly flow; to maintain the flow, you need to complete the circuit so you can reuse electrons or attach the coil to "ground" where the circuit is completed so other electrons may be utilized and reused. As noted above, the copper mass is not depleted, rather electrons must be reused and or supplied via another source. Normal low voltage EMF's are not strong enough to force strongly bound electrons from their atoms...

    In the case of a battery source, electrons leave one terminal and return via the other terminal for reuse....lift a terminal and electron flow stops...no power can be delivered...within a battery chemical processes push the electrons along and provide the power use use externally.

    As perhaps you know, the Power is EI or I^2(R)... so however the electrons are forced to move, their flow q= it enables work to be done......hard as it is to visulaize, electrons can deliver large amounts of power from a source to a distant load...long distance high voltage transmission lines carry very high voltage so as to reduce current flow...less electrons flow....hence reducing losses which are I^2(r) where r is the resistance of the transmission cable. The electrons are reused here via ground: transmission lines carry only the positive leg of the circuit; the negative is the earth itself!

    Pretty crazy, actually, and this was not theoretically conceived, I don't think, it was Faraday who figured out a lot of it experimentally. At the time electricity was "discovered" maybe in electric eels!!!! people did not even know about atoms and electrons.
  17. Nov 3, 2008 #16
    The concept you stated about copper "breaking down" DOES happen in other environments.
    Galvanic (crevice) corrosion is an example.....

    Brass is an alloy of copper and zinc. When placed in salt water current (electrons) flow from the metals and a battery is created whenever zinc and copper are in close proximity...Zinc WILL give up it's electrons and be depleted...pinholes will appear in the brass and this deterioriation is called crevice corrosion. The zinc deterioriates weakening the entire alloy...leaks may develop...eventually you may be able to crumble the metal (alloy) by hand....Hence brass is a bad alloy to use in salt water; instead bronze alloys which mix copper and tin are quite stable....they don't easily give up their electrons, so hardly any corrosion occurs. Tin and copper are close enough on the galvanic scale of potential so they don't give up electrons in proximity....metals used in batteries should be far apart and inexpensive and durable to enhance electron flow....most have been determined by trial and error....
    This propensity of zinc to give up electrons can be used to good advantage: By placing zinc anodes (bolting on lumps of zinc) on underwater metal parts, they are protected since the zinc gives up its electrons easily protecting the important structural metals.
  18. Nov 3, 2008 #17
    According to the basic laws of physics, every wavelength of electromagnetic radiation corresponds to a specific amount of energy. Thus, with Einstein equation, E = mc2, we can derive that m=E/c2. Thus energy has mass, and this mass is coming from somewhere.

    I think I understand the concept that electrons are being replaced in the circuit. Very interesting. So, the copper never loses mass its just the free electrons that are being replaced that come from the surrounding environment? right?
  19. Nov 3, 2008 #18


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    This really is a misapplication of the concept. All that equation says is that a certain amount of mass CAN, in principle, be converted to an equivalent form of energy. Or that a certain amount of energy can be converted, under the right condition, into mass.

    However, this is NOT the whole story because there's a slew of conservation laws that come with the ride! You can't simply say that an electron is nothing more than energy, because energy (i.e. photons) cannot be compressed together to create a lepton with spin 1/2, no matter how hard you try.

    Thus, to make a cavalier statement that energy has mass, and mass has energy, is a severe misunderstand and misapplication of that equation (read the FAQ).

  20. Nov 3, 2008 #19
    Ok here's the deal,

    I did some research on "can electromagnetic energy be converted into mass". I also went and talked to a professor at the local university. There are studies and experiments that show that electromagnetic energy can be converted into electrons and positrons which have mass characteristics. My professor agrees with this statement. Current physics has no idea what mass really is. This is why they built the haldon collider. In fact, I have learned that the pure kinetic energy of the photons being collided together produce additional particles that have mass characteristics. E=mc2 is a direct correlation to these concepts. One must first figure out what mass really is, then we can figure out what energy really is. You can't just say that electromagnetic energy can't be converted into electrons because we don't even know what an electron really is. There are probably billions and billions of subatomic particles that we don't know about yet. These particles, and this is just a theory, make up the forces and matter that we think we can explain.

    I hope we can have a better understanding of where electrons come from with experiments being conducted at the haldon collider.

  21. Nov 3, 2008 #20


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    This is completely different from what you were asking about originally: electrons in a classical electrical circuit driven by electromagnetic induction or some other means. In those situations, pair-production of electrons and positrons plays no role at all.

    We don't need new discoveries at the LHC to help us explain how ordinary electric circuits work. :eek:
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