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Where from energy came

  1. Mar 13, 2012 #1
    my understanding is this

    a generator push electron and they go to Bulb,now few electron will make the resistance and light will produce.rest of electron will go back in circuit.

    let us say generator produce 100 electron and blub use 50 electrons rest of 50 electron will come back.
    from where the generator will produce more electron for continuous supply of electron???????

    if you say copper wire has free electron,even then my question is 50 electrons used to light blub, this will make 50 electron of copper wire to use in light energy ,generator does not create electricity,from where more electron comes in copper wire?????

    are electrons moving freely all around us other than around atoms,if yes then it means we are surrounded by free electrons???? and in generator generator force these free electrons from surroundings to go in copper wire?????

    where from more electron coming in circuit?????

    and if no electron coming from surroundings and there is no loss of electron in blub rather generator give energy to electrons and these electrons deliver this energy in blub in the form of light and then go forward charge free i.e before they coming into blub they carry some energy given them by generator ,and after delivering this energy into blub they move on free of energy and then go back into generator and regain energy from generator?????
    right ?????
    Last edited: Mar 13, 2012
  2. jcsd
  3. Mar 13, 2012 #2
    the generator is lets say Pushing(volts) electrons from the generator to the light bulb(load). the free elctrons in the copper wire allow the wire to be a "conductor" rather than an insulator. thats why we dont use hammer handles to light light bulbs. :D
  4. Mar 13, 2012 #3

    jim hardy

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    Be very careful with this mental picture.

    Indeed the electrons drift along the wire but very slowly.
    What does move fast is the (electromotive)force that pushes an electron out one end of the wire almost immediately after one is pushed into opposite end of wire.
    They're not the same electron.
    If the electrons approach 1m/sec the wire has long since overheated and melted.
    They just bump one another along, moving perhaps one atom per bump.

    What you are asking is the basis of Kirchoff's current law.
    Current gets back to where it came from.
    But not every individual electron does,
    they drift slowly like an army of ants going around in a circle , millions abreast..

    That's an oversimplification.
    Hopefully it will help your mind accept Kirchoff's laws at this point in your studies.
    We refine our mental picture as our understanding increases.

    Very Good ! That's what a VOLT is, a joule per coulomb.
    Look into conversion factor between electron volts to joules
    and amount of charge in a coulomb.
  5. Mar 13, 2012 #4


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    What was the source that produced this 'understanding'? It has some very dodgy ideas in it and you would be better to read something a bit more 'mainstream' than any source that had just those ideas in it.

    It may annoy you but 'Electrons' are really not the best way into understanding Electricity. This is because they just do not behave in the way that they tell kids in School and you need to unlearn a lot of that stuff if you really want to get on with Electricity and Electronics. Of course they are involved in conduction but not in the way you describe.

    Electronics is much more easily treated as a 'black box' subject which works to a very limited set of simple rules. If you try to impose the flawed model of electrons into simple circuit theory it will lead to confusion.
  6. Mar 13, 2012 #5


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    Hi mashood. Electrons don't get "used up" in electric circuits. Electrons are matter, and only in nuclear reactions does matter get "used up".

    Electrons in an electric circuit just keep going around and around, jostling each other along as they feel the nudge of the emf in the generator. During the time that the generator pushes 100 electrons along its negative terminal wire, exactly 100 will emerge from the other end of that wire and flow into the positive terminal of the generator. For every electron that leaves, another one returns. :smile:
    No more come from anywhere. They don't need to--the same ones just keep getting recycled, around and around!

    Electrons are free, it's pushing them around that requires energy. :wink:
  7. Mar 14, 2012 #6
    thanks all of you to make my understanding much more clear i am thankful,i think a lot of these concepts require quantum mechanics.
  8. Mar 14, 2012 #7
    Hi, mashhood, yes you are correct that, a deeper understanding might call for quantum mechanics. But either way its all about how deep you want to go. And there is limit.
    But for most parts for understanding Electricity things, 'black box' theory suggested by 'sophiecentaur' is very good.

    To explain what that means, suppose you want to study how a system comprising of a generator supplied light bulb works.
    You can take any of the following as granted.
    1) Generates produce voltage when rotated by prime mover.
    2) A st. Conductors generate Emf in moved in a magnetic field.
    3) Moving charged particles are deflected by magnetic field.

    2 follows from 3 And 1 follows from 2.
    You don't absolutely need 2 and 3 unless you want to design and repair Generators. You can go about solving complex power systems without them.

    Similarly you can assume any of the following.
    1) i) In a resistive circuit, Current I = V/R and heat = I^2*R
    ....ii) R = rho*L/A where the resistivity (rho) is an intrinsic property of the material,

    2) i) Electrons are accelerated under electric fields
    ....ii) In conductors there are pools of free electrons
    ....iii) When electric filed is applied across conductor the electrons accelerates, but constantly bounce with each other and the core atoms. This generates heats and how much heat is generated is dependent on the electron density etc.

    'sophiecentaur' was suggesting you to assume 1) instead of dwelling in 2).

    Choosing 1. in above examples, is accepting 'black box' models.
    Last edited: Mar 14, 2012
  9. Mar 15, 2012 #8
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