why chages move towards the surface of the conductor,as we increase the frequency of a.c(skin effect)?

Question

I know what skin effect is ,but i want to know why charges behave like that when we increase the frequency of the a.c signa?any body who can help me ?

Answer 1

When sound (or other waveform of similar shape, like an AC signal) travels through a medium, its intensity diminishes with distance. In idealized materials, signal amplitude is only reduced by the spreading of the wave. Natural materials, however, all produce an effect which further weakens the sound. This further weakening results from scattering and absorption. Scattering is the reflection of the sound in directions other than its original direction of propagation. Absorption is the conversion of the sound energy to other forms of energy. The combined effect of scattering and absorption is called attenuation. Ultrasonic attenuation is the decay rate of the wave as it propagates through material.

Attenuation of sound within a material itself is often not of intrinsic interest. However, natural properties and loading conditions can be related to attenuation. Attenuation often serves as a measurement tool that leads to the formation of theories to explain physical or chemical phenomenon that decreases the ultrasonic intensity.

The amplitude change of a decaying plane wave can be expressed as:

A = A0*e^(-kz)

In this expression "A0" is the amplitude of the propagating wave at some location. The amplitude "A" is the reduced amplitude after the wave has traveled a distance "z" from that initial location. The quantity "k" is the attenuation coefficient of the wave traveling in the z-direction. The dimensions of are nepers/length, where a neper is a dimensionless quantity. The term "e" is Napier's constant which is equal to approximately 2.71828.

Attenuation is generally proportional to the square of frequency. Quoted values of attenuation are often given for a single frequency, or an attenuation value averaged over many frequencies may be given. Also, the actual value of the attenuation coefficient for a given material is highly dependent on the way in which the material was manufactured. Thus, quoted values of attenuation only give a rough indication of the attenuation and should not be automatically trusted. Generally, a reliable value of attenuation can only be obtained by determining the attenuation experimentally for the particular material being used.

This is why higher-frequency signals tend to produce what is called "skin effect" ... basically, the energy isn't there for the wave to penetrate to any significant depth.

Answer 2

I think in high frequency, you need to reduce the effective conduction area to reduce overlapping of electrons