Discusión:Efecto pelicular

resistencia o impedancia

La oposición que un cuerpo opone al paso de una corriente alterna se llama IMPEDANCIA que a su vez esta compuesta por la RESISTENCIA (parte real de la misma) y la REACTANCIA, capacitativa o inductiva, (parte imaginaria). Al variar la frecuencia, varia la reactancia (ya que depende de esta) y por lo tanto la impedancia total del circuito. A un frecuencia determinada la reactancia de un circuito se anula (la capacitativa y la inductiva son iguales y de signo contrario) entonces se dice que ese circuito ha entrado en resonancia y a esa frecuencia se le llama frecuencia de resonancia. POr esto creo que lo que pone en el articulo no es del todo corecto. POr otro lado las cargas electricas siempre circulan por la superficie del conductor independientemente de la frecuencia, incluso en estatica las cargas se situan en la superficie, en este fenomeno se basa el generador de Vander Garaf. Con la esperanza de que estas líneas sirvan para mejorar este artículo Un saludo--Txo (discusión) 18:58 3 mar 2006 (CET)

Hola Txo, permiteme una puntualización en tu afirmación de que las cargas eléctricas siempre circulan por la superficie. Es cierto que cuando no hay circulación de cargas (no hay corriente eléctrica, es decir en electroestática), las cargas se sitúan en la superficie. Sin embargo este artículo es sobre el efecto pelicular que se produce en electrodinámica, es decir cuando hay movimiento de cargas y además cuando se trabaja con corrientes variables (por ejemplo en AC), en cambio cuando se trabaja en corriente continua la carga fluye por toda la sección del cable.

He encontrado este artículo que lo resume de una forma bastante clara:

(obtenido de aquí http://amasci.com/miscon/eleca.html#surf )

ELECTRIC CHARGES ONLY FLOW ON THE SURFACES OF WIRES? Wrong.

During a Direct Current in a simple circuit, the flow of charges takes place throughout the whole wire. The flow is not just on the surface. If the level of current is very high, then the wire will become hot, and the current will heat up the inside of the wire as well as its surface. Thin hollow pipes make poor conductors; their electrical resistance is too high. To avoid overheating the metal we should use thick solid bars instead.

There is a persistent 'rumor' that the path for flowing charges is entirely on the surface of metals. This mistaken idea probably comes about through a misunderstanding of the nature of electric charge. After all, when some electric charge is deposited onto a metal object, it distributes itself over the surface of the object. It makes sense that, since charge is only on the surface of metals, a flow of charge must take place only on the surface of metals, right? Wrong. 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 movable charge inside, even though they may be "neutral" and so have zero charge on average. Are you confused yet?

All metals contain enormous amounts of free, movable electrons. During an electric current it's these electrons which flow along. 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 this "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. The currents inside the "ocean" would be unaffected. Yet extra charges on a wire also 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 surface charges are the metal's only charges. Yet in reality, electric currents happen in the "ocean" of the wire, and the extra "teacup" of unbalanced charge on the surface has little effect on the overall charge-flow. The charge-flow (current) is not just on the surface, and during electric current, the whole "ocean" flows.

A second source of misunderstandings: during high frequency AC, the value of electric current in 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 very important for thin household wires at 60Hz. Perhaps some people heard about the Skin Effect but did not realize that it only works for very thick wires or for high frequency AC. At extremely high frequencies, only the charges in a thin "skin" on the surface of large wires are the charges which move. For circuits involving high-current and high-frequency such as radio transmitters, it makes sense to use copper pipes as conductors. All the charge-flow is on the surface of the conductors, so use inexpensive hollow conductors. All the heating takes place on the surface, and not deep within the metal. But note well that the thin "skin" of current is a *different* thing than the thin "skin" of excess charge-imbalance found on an electrified wire.

Perdón por contestar a los 10 años de la publicación de tu comentario pero era necesario puesto que he considerado la información incorrecta.

Un saludo, Terraco

densidad pelicular

abajo se define la densidad pelicular como un "area" y luego se da una fórmula cuyas unidades son metros.

una definicion mas precisa podria ser:

"la profundidad debajo de la superficie del conductor en la cual la densidad de corriente decae a 1 / e (cerca de 0,37) de la densidad de corriente en la superficie (JS)."