Does an alternating current have surface charges associated with the current charges?

Question

As alternating current passes along a wire:

• Different charges are pushed to the surface in response to the current charges and form an excess electric field, leaving the interior wire neutral.

Questions:

1. Is this view correct?

• This would mean there are two groups of charges.
• Experimentally: Is there a strong electric field associated with each half wave even with a low resistance wire?

2. Does the electric field travel down the wire near the speed of light and, before a current starts, all the positive and negative half waves are established along the length of the wire. The current charges between half waves can then neutralize each other. All the half waves progressively change together near the speed of light as the alternating electric field refreshes. Charges do not form on the surface in response to current charges.

• This can mean there is not an electric field associated with each half wave. There can still be an electric field from resistance in the wire deflecting current charges to the surface.

Answer 1

From Gauss' law we get the fact that there is no field inside a closed conductor. this puts the unbalanced charges on the surface of the wire in response to the local charge-imbalance on that wire.

In large conductors the skin effect puts most of the alternating current near the surface of the wire, but that's a magnetic effect.

As alternating current passes along a wire:

A wire long enough to present even a half wave of AC is not a mere wire anymore, it's now a transmission line, and new emergant behaviours come from the wave properties of signals in wires.

Is this view correct?

The picture is a nonsense. but see Gauss' law.

This would mean there are two groups of charges.

Not really, it's all one pool of conduction band electrons, if only the surface electrons carried the charge then the bulk of the wire would not conduct current. as the potential in the wire increases caused by current flowing in the bulk of the wire charges are pushed to the surface of the wire

the distance traveled by most charges in a wire carrying domestic AC is just a fraction of a millimeter before the current reverses, in an antenna carrying radio frequency it's even less.

Also note that potential and current need not be synchronised.

Experimentally: Is there a strong electric field associated with each half wave even with a low resistance wire?

A strong external field? Yes, that's how non-contact voltage detectors work. also electrostatic loudspeakers etc. Internally, no, See Gauss's law.