ELECTRIC CHARGES ONLY FLOW ON THE SURFACES OF WIRES
November 15, 2010 2 Comments
Wrong. The flow of electricity along a wire is a form of dissipation of electrical pressure and therefore generally tends to be a surface phenomenon, flowing over the greatest surface area, which offers the least amount of resistance, and which forms the pressure boundary. Though thin, hollow metal pipes usually make poor conductors as their capacity to carry a current is low. In solid conductors the electrical pressure will flow through the entire conductor if there is sufficient resistance in the form of limited capacity on the surface. It is this reason it is better to use solid wires which offer greater current carrying capacity and are less prone to overheating.
Rather than “conducting” it would be better to think of the conductor as a channel where electrical pressure can be dissipated in the same way a flood would spread across a landscape flowing along the path of least resistance.
Personally I disagree with the electron theory as I have outlined in “Electrostatic Theory is Wrong”, but William Beaty explains the present electron theory in relation to this subject well…
“Unfortunately, the word “charge” refers to two different things. When electric charge is placed on a metal object, the added charge is just a drop in the bucket compared to the amount of charge already in the neutral metal. “Uncharged” wires contain an enormous amount of charge, even though they may have “zero charge” on their surfaces. Confused yet? All metals contain huge amounts of movable electrons. During an electric current it is these electrons which flow. However, each electron is near a proton, and so the metal is said to be “uncharged.” In a wire, electric current is a flow of “uncharged charge”. Weird but true. Now if we were to place EXTRA charge upon a wire, that would be like pouring a teacup into the ocean. The “water level” would rise a tiny bit. Yet extra charges on a wire create a very noticeable electrical imbalance (they attract lint, deflect electroscopes, make sparks, etc.) It isn’t so strange that we might accidentally assume that the extra charges are the only charges there. Yet in reality, electric currents happen in the “ocean” of the wire, and the extra “teacup” has little effect on the charge flow. The charge flow (current) is not just on the surface. A second source of misunderstandings: during high frequency AC, the electric current on the surface of a conductor is higher at the surface than it is within the bulk of the metal. This is called the “skin effect.” It is not important for everyday wires at 60Hz. Perhaps some people heard about the Skin Effect but did not realize that it only works for high frequency AC. At extremely high frequencies, the current does flow as a “skin” on the surface of large wires. For high-current, high-frequency circuits such as radio transmitters, it makes sense to use copper pipes as conductors. All the charge flow is on the surface of the conductors. All the heating takes place on the surface, and not deep within the metal.”