What causes skin effect in AC currents?

  • #1
Qmavam
15
3
My assumption has been it is the electromagnetic field starting from the center of the wire that pushes the electrons outward.
However, this would also be true of a DC current, but it isn't.
So why does an AC current cause electrons to move toward the skin of a wire?
I don't recall ever seeing this explained.
Thanks, Mikek
 
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  • #2
Qmavam said:
So why does an AC current cause electrons to move toward the skin of a wire?
It does not.
The current starts on the outside surface, and moves slowly into the conductor.

The incident loop of magnetic field, around the wire, causes a current to flow along the wire.
That causes an opposite magnetic field loop, that cancels most of the incident field, which reduces the magnetic field entering the conductor, and so the current stays on the surface.
 

Related to What causes skin effect in AC currents?

What causes skin effect in AC currents?

Skin effect in AC currents is caused by the tendency of alternating current (AC) to distribute itself unevenly within a conductor, with higher current density near the surface. This phenomenon occurs because the changing magnetic field created by the AC induces eddy currents within the conductor, which oppose the flow of the main current. As a result, the current is forced towards the outer edges of the conductor.

How does frequency affect skin effect?

The skin effect becomes more pronounced at higher frequencies. As the frequency of the alternating current increases, the depth at which the current can penetrate into the conductor decreases. This is because higher frequency currents induce stronger eddy currents, which in turn create a greater opposition to the main current flow, pushing it closer to the surface.

Why is skin effect less significant in DC currents?

Skin effect is less significant in direct current (DC) because DC does not change direction and therefore does not generate the varying magnetic fields that induce eddy currents. Without these eddy currents, the current is distributed more uniformly across the entire cross-section of the conductor.

What materials are most affected by skin effect?

Conductive materials with high conductivity, such as copper and aluminum, are most affected by skin effect because they allow for stronger eddy currents to be induced. However, all conductive materials exhibit some degree of skin effect when subjected to AC, with the extent depending on their electrical properties and the frequency of the current.

How can skin effect be mitigated in practical applications?

Skin effect can be mitigated by using conductors with larger surface areas, such as litz wire, which consists of many thin, insulated strands woven together. This increases the effective surface area and allows the current to distribute more evenly. Additionally, using materials with lower conductivity or operating at lower frequencies can also reduce the impact of skin effect.

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