Why High frequancy cause high resistance

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    Cause Resistance
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Discussion Overview

The discussion revolves around the relationship between frequency and electrical resistance, particularly in the context of conductive materials. Participants explore theoretical models and physical phenomena that may explain how resistance changes with increasing frequency.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about a mathematical equation or law that describes the increase in resistance with frequency.
  • Another participant references the Drude Model, explaining that it suggests conductivity remains relatively stable at low frequencies but decreases significantly at higher frequencies due to rapid electron scattering.
  • A different participant mentions that at high frequencies, electricity primarily conducts on the surface of a metal wire, implying this contributes to increased resistance.
  • A link to the Wikipedia page on the skin effect is provided, which may further elaborate on the surface conduction phenomenon.

Areas of Agreement / Disagreement

Participants present multiple perspectives on how frequency affects resistance, with no consensus reached on a singular explanation or model.

Contextual Notes

Some assumptions about the materials and conditions under which these phenomena occur are not explicitly stated, and the discussion does not resolve the mathematical details or implications of the models referenced.

dumty
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well i have a question in my mind.
is there any mathematical equation or law that shows how the resistance increases as we increase the Frequencies.
 
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In fact, there is. One of the simplest models of conductivity is the Drude Model, which assumes that electrons in a solid move freely when an electric field is applied, but are scattered by collisions every so often (with an average lifetime called the scattering time). Surprisingly, it works pretty well for many materials. Wikipedia has a page on it which gives the differential equation and resultant conductivity equation.

Essentially, the conductivity doesn't change by very much at low frequencies, but for frequencies on the order of 1/(scattering time), it drops quickly. Physically, what this means is that for high frequency signals, electrons are getting scattered so quickly that they don't really have a chance to respond to the field.
 
I have read at high frequencies, a metal wire only conducts electricity on the surface, that's why the resistance increases.
 
http://en.wikipedia.org/wiki/Skin_effect"
 
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