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What exactly is voltage?

  1. May 5, 2005 #1
    I'm currently in college at the moment and of course in high school we did all these stuff about electricity and I got through that alright.

    But now I'm getting bugged: what exactly is voltage?

    Sure V = Joules/coulomb so can one treat it as the energy "carried" by an electron? If so, shouldn't this raise the eV?(but then electron drift is such a slow process). And when electrons return to battery(the plates) shouldn't it gain KE (in eV) equivalent to the voltage of the battery.(Since you are putting an electron between two charged plates)

    Very newbie question, but its one of those that lingers over your head and just makes you feel that little bit uncomfortable.
  2. jcsd
  3. May 5, 2005 #2


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    Staff: Mentor

  4. May 5, 2005 #3
    If electrons travel (in vacuum) between the plates of a capacitor they will gain an KE of e times the potential difference when reaching the opposite plate. They will lose this KE in one collision with the opposite plate.
    If electrons travels through a conductor they will collide with the atomic lattice after a very small distance (~10^-6 meter) thereby losing their gained KE. So they are slowed down all the time. In the end they still gained exactly the same energy but their speed is now much slower because of the many collisions. Does this make any sense?
  5. May 6, 2005 #4


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    think of a coulomb of charge as a gallon of water. then current would be gallons per second (that makes sense, no?) and voltage would be the measure of how much potential energy each gallon has. a gallon lifted up to the top of a water tower has more potential energy (the potential to do a lot of damage) than one down here on the ground. this is why water pressure can be related to voltage.

    all that battery is, is a sorta pump that lifts the coulombs from a low potential energy state to a higher potential energy state.

    likewise, a coulomb of charge at a high voltage (or high potential energy) can have more potential to do work (or harm) than a coulomb at low voltage.

    maybe that was too basic.

    r b-j
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