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How is electrical potential transmitted through an electric circuit

  1. Nov 15, 2004 #1
    My question is how is electrical potential actually transmitted through an electric circuit.

    A charge (i.e. and electron) is moved through an magnetic field (as in a generator), the particle gains electric potential due to the work performed on it in the generator. This potential is then used elsewhere in a circuit (e.g. a motor or transformer) to do useful work.

    How is the potential acually stored in the electron? If this were a gaseous system, the potential would be represented as an increase in pressure, manifested as higher temperatures and tighter packing of the molecules. If this were a physical system, the potential energy might be manifested as balls lifted higher in a gravitational field, capable of doing work as the fall.

    What is the mechanism for our electron? Faster motion or increased vibration?

    Thanks.
     
  2. jcsd
  3. Nov 15, 2004 #2
    Hmm, I say it's by the movement of electrons throughout the circuit. The more electrons that are pushed through the circuit, the more potential energy it has. So, the more voltage you supply to the circuit, or the larger the battery, the more potential energy it has.

    I say that a single electron stores potential energy by it's velocity, but with circuits, we're talking about tons and tons and tons of electrons moving at the same velocity, so it's the amount of electrons that account for the potential energy.
     
  4. Nov 15, 2004 #3
    Thanks for the thoughts, but electric potential is not related to the amount of electrons. The electric potential is measured in V (volts) which is joules per coulomb or energy per unit charge. Since each electron has the same charge, this is the equivalent to saying energy per electron. The amount of charges (electrons) is the current, I, in coulombs per second. In an electrical circuit, you can use a transformer to convert a large amount of one into a large amount of the other, but they are two separate things.

    Thinking back to the ball example, the potential (voltage) is the height that we have lifted our ball. The current is the quantity of balls that we have lifted. You can use two balls lifted to a height of one meter to lift a single third ball to a height of two meters.

    So you can have two wires, each carying one amp of current, but one wire is at one volt, and the other at two volts (relative to ground). Both wires are transporting the same quantity of electrons, but the electrons in the two volt wire each contain twice as much energy as the electrons of the one volt wire.

    What I want to know is what is different about these two volt electrons that acutally gives them more energy?
     
  5. Nov 15, 2004 #4

    ehild

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    Two electrons at different electric potential differ as much as two identical balls at different height. The balls are at points of different potential in a gravitational field, the electrons are at points of different potential in an electric field. You can imagine mass as "gravitational charge". Charges get potential energy in a field. If they move in the field between points of different potential the potential energy difference will be transformed into other kind of energy - kinetic energy, heat...

    ehild
     
  6. Nov 15, 2004 #5
    Energy is simply motion ( with mass) , therefore if there is more energy there is more motion , this maybe due to speed ( average ) or due to amount , as you say voltage is energy PER unit charge there fore it implies higher motion of the charge ( electron ) -- so I think you have answered your own question. Ray
    Vibration ( spin ) or whatever is a different matter in electronics we are dealing with translational energy and losses due to interaction with the sub lattice ( heat ).
     
  7. Nov 16, 2004 #6

    krab

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    This is an electrical system; potential is stored in the electron by the electron being at a location that has a certain electrical potential. To use your words, electrons are lifted "higher" in an electrical field, capable of doing work as they fall in this electrical potential. It is exactly analogous to gravity, except that charges are either sign and forces can be attractive or repulsive, whereas mass is one sign and force there is always attractive.
     
  8. Nov 16, 2004 #7

    reilly

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    First of all, electrons do not store potential energy. If an electron is in a force field, then at every (appropriate) point in space there is a specific force -- electrical, gravitational, magnetic, ... --- which acts on the electron, and which is generated, solely, by some source -- generator, battery, charge complex, matter complex, .... For conservative forces, there is, by definition, a well defined potential, precisely specified modulo a constant.

    Then, there are non-conservative forces. For example, in a time-varying E&M situation, the electric field is generated by a time-varying magnetic field, as well as, posssibly by a charge complex.

    The thing to remember is simply: for a current to exist, there must be a force acting on the charge carriers. If the force is conservative, there's a well defined potential. If not, then the force is classified as an electromotive force. All of this is usually discussed in exquisite detail in freshman physics books -- batteries, generators, maybe more subtle situations like thermocouples, piezoelectric effects, and so forth.

    Often, electric circuits afford a student's first experience with non-conservative forces (other than friction) Tricky, but most get the ideas after a bit of study.

    Regards,
    Reilly Atkinson
     
  9. Nov 16, 2004 #8
    I always get that confused, thanks for the explination Quercus. Ok, the electric potenital energy depends on the position of the electron in an electric field, the same way the potential energy of the ball depends on the height of the ball above the earth's surface.

    Ex: Take a uniform electric field and point it down and put a positive test charge into the field...similar to a ball in the earth's gravity field. If you move the test charge up, the E-field does negative work on the charge, so the charge gains potential energy, the same way the ball gains potential energy when it's raised up.
     
    Last edited by a moderator: Nov 16, 2004
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