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B Where Is The Voltage?

  1. Jan 10, 2019 #1
    If we can look at all the atoms in a copper wire between a point of zero volts and a point of, say, 10,000 volts and observe no difference in any of the atoms then where is the Voltage?

    Is it perhaps as with the kinetic energy of a brick raised to a great height with respect to the earth - a manifestation of the work done to move against the acceleration of gravity? i.e. the gravitational 'force' ?

    And in the case of electricity an 'electromagnetic force' ? i.e. a field that we observe only through its effects upon certain things we put in the field?
     
  2. jcsd
  3. Jan 10, 2019 #2

    jbriggs444

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    How are you maintaining a 10,000 volt potential difference in a conductor?

    "Voltage" is a measure of electrostatic potential with respect to some chosen reference. If there is a potential difference, there is a field. That field will tend to propel free charges that exist within it -- such as electrons in a copper wire. Those free charges will move. Current will flow and the potential difference will drain away.

    The underlying definitions for "potential" and "field" involve vector calculus. If you have not been introduced to those concepts, one way to think of it is by analogy.

    Voltage is like the height of a point on a hill.
    Electromotive force at a point is like the slope of a hill at that point.
    An electron is like a ball on the hill. Unless held in place, it will roll to the bottom.

    A ball on a hill rolls down the same way no matter whether the hill is in the middle of a high plateau or in the middle of Death Valley.
     
    Last edited: Jan 10, 2019
  4. Jan 10, 2019 #3

    Dale

    Staff: Mentor

    The voltage is in the fields. The voltage difference is not about the copper atoms themselves, it is about their location in the electric field.

    Similarly a rock at the top of a hill may be in every respect identical to a rock at the bottom of a hill. The difference in gravitational potential is due to the rocks different locations in the gravitational field.
     
    Last edited: Jan 10, 2019
  5. Jan 11, 2019 at 8:24 PM #4
    Thank you.

    And a gravity field is the very shape of time and space.

    What is an electric field?
     
  6. Jan 11, 2019 at 8:32 PM #5
    Think of voltage as pressure in a water line. The molecules of water at one end of the line are no different than the molecules at the other end of the line. However at the high pressure end they are bump into each other a lot more. In a wire, the particles generating the voltage are the electrons. And as an aside, the resistance to flow is very low in copper - the electrons don't lose much energy moving through the copper. so they have to travel very far through a lot of copper before they start bumping into each other less ( the voltage drops). And of course all that bumping creates heat.
     
  7. Jan 11, 2019 at 8:52 PM #6

    Drakkith

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    A field is a way of representing something that has a value at different positions in space. For example, your weatherman uses a temperature field that keeps track of temperatures at different cities. The same can be done with many different quantities, such as wind, rainfall, etc.

    The electric field is a way of representing what will happen to electrically charged particles. Using it, we can say what will happen to a test particle when placed anywhere within a certain region. More specifically, it gives us the direction and magnitude of the force that the test particle would feel when placed anywhere in the region of space that the field is describing.
     
  8. Jan 12, 2019 at 2:20 AM #7

    davenn

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    no, not even close
    please go do some reading on potential difference, electron flow ( more specifically the flow of charge)
    free electrons in a conductor, electric field
     
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