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Negative electrical potential

  1. Apr 11, 2008 #1
    Is there such a thing in electrical circuits, or anywhere else? Or is this just considered reverse polarity, or 0V?
    Last edited: Apr 11, 2008
  2. jcsd
  3. Apr 11, 2008 #2
    Potential is always relative to an arbitrary reference of 0. Positive potentials are used more than negative, only because it is more convenient.
    In electric circuits, and with DC we just call the negative side of the voltage source 0V. If there's only one voltage source, all the potentials will be positive relative to this.
    Electric circuits wich use a power supply that deliver -V, 0 and +V are also used however.
    With Electrostatics, often 0V is assigned to a point infinitely far away. You will then get a positive potential close to a positive charge, and a negative potential close to a negative charge.
  4. Apr 12, 2008 #3


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    Staff: Mentor

    The polarity of charge is arbitrary. By convention, we have establish the charge of electrons as - and that of protons as +.

    A collection of electrons will by definition produce a negative potential with respect to some neutral (equal numbers of electrons and protons) set of charge, and an absence of electrons or excess of protons or even positrons, would have a positive potential with respect to a neutral or negative charge.

    The electric field points from + to -.
  5. Apr 12, 2008 #4
    I thought that might be the case with ions.. negative charged atoms (electrons) create negative potential, and positive charged (holes) atoms create positive potential, and that potential difference is measured in voltage?

    This leads to my next question: In a battery (dipole), is there a negative and positive potential working to move current? Wouldn't a true dipole require both + and - charge, it seems strange that batteries are only seen as having 0V and +V .
  6. Apr 12, 2008 #5
    this negative potential that u are talking about is something that u've compared to infinity as if infinity has 0 potential, it is perfectly legal to say that negative charged particle create 0 potential at some point in space if u assign some positive potential value to thet 'infinity' place
  7. Apr 13, 2008 #6
    Do physicists consider batteries to be electrical dipoles?
  8. Apr 13, 2008 #7
    As mentioned above the zero value of the electric potential is typically set to zero in those cases in which the electri potential falls to zero at infinity. However there are instances one runs into when working problems in electrostatics. For example; if you were studying electrostatics then a well-known problem is to find the electric potential of an infinitely long line of charge which has a uniform linear charge distribution. In this case the electric potential does not go to zero at infinity. The zero potential is then chosen to be at an arbitrary distance from the line of charge. Closer to the line the electric potential is zero, further from this distance the electric potential is positive.

    Notice that the absolute value of the electric potential has no physical meaning. It is the variation in space of the electric potential which has a physical meaning. The physical meaning being that E = [itex]\grad \phi[/itex]. Any constant added to the electric potential will drop out in when the gradient is applied (since the value of the gradient of a constant is zero).

  9. Apr 14, 2008 #8
    Sorry I'm having such difficulty understanding this. So positive / negative potential isn't really a component of electromotive force, and isn't considered a force that moves charge in a short circuit? I keep trying to visualize what is physically happening in the circuit.
    Last edited: Apr 14, 2008
  10. Apr 14, 2008 #9
    u can picture potential as actual field with hill, therefore u can assign the zero value to any height and call those place lower in height to the place that u assigned zero value as having negative potential and those places higher than the zero valued are considered having positive potential, and of course, when u roll a ball, they will roll down from a higher place in this hill to someplace lower, right? In our case if the hill is the potential, the ball is the electron and the force that is pulling the ball is the electric field

    hope i was helping
  11. Apr 14, 2008 #10
    Thanks, thats what I thought. But is it possible 'negative potential' gives the hill an even stepper gradient at the negative side of the circuit, performing work? i.e, on a 12V battery, If negative charge can push electrons, then 0V would be misleading. And if positive charge can pull only contribute to 1/2 the EMF, then +12V would be strange as well. If this seems too weird/off let me know.

    Also, what do you think about the battery dipole questions?
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