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Electrostatic potential from the perspective of an electron

  1. Sep 9, 2010 #1
    Thinking in terms of electric circuits and electrostatic potential I understand how an electric current arises as manifestation of a difference in potential. How does this work at a more microscopic level? I.e. how does an electron know what potential it's environment is at?

    E.g.: If I, standing on the earth, connect myself to a power plug, the electron in the wire just inside the wall will run through me. If I stand on some insulating material however, the electron will not. How precise is this? I.e. will there be virtually not a single electron penetrating my skin?

    If a bird sits on a power line he "takes over" the potential of the power line (thereby avoiding any current through his body), right? Does this have any implications on a physiological level?

    Looking forward to your thoughts...Cliowa
     
  2. jcsd
  3. Sep 9, 2010 #2

    jtbell

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    Staff: Mentor

    An electron doesn't "feel" the electric potential at a point, any more than you "feel" the gravitational potential at the location where you're standing. That is, you don't "feel" any different standing on the first floor of a building than on the second floor, even though the second floor is at a higher graviational potential.

    What the electron actually "feels" is the electric field E that acts on it, which is the gradient of the electric potential. The electric field produces the force which makes the electron move, via F = qE.

    Inside a uniform wire with a fixed potential difference between its ends, the electric potential decreases steadily as you move from one end to the other, i.e. the gradient of the potential is uniform, and so is the electric field.
     
  4. Sep 9, 2010 #3
    I agree completely. What puzzles me is rather the way the electrostatic potential can be "acquired" through contact. Example: A bird that first sat on some tree (which has the same potential as the earth) and then flies off to a power line, where he (suddenly?) "acquires" the potential of the power line.

    Again: Is is really true that not a single electron from the power plug will penetrate my skin if I stand on some completely insulating material?
     
  5. Sep 9, 2010 #4
    No, by touching a wire, a current will flow into you until you are at the same potential as the wire. At this point, the charge that you have acquired is equal to your capacitance times the voltage. With a wire at thousands of volts, you will therefore feel a jolt. It can seen that it is hazardous to touch a high voltage AC wire, since the current will never stop.
     
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