MCQ Detailed View

The correct unit of electrical conductivity is Siemens per meter (S/m), which was historically referred to as mho per meter. The term "mho" was used because conductivity is the reciprocal of resistivity, and the ohm (Ω) represents resistance. Writing "ohm" backward gives "mho," symbolizing the inverse relationship. However, the modern SI unit is Siemens (S).

Electrical conductivity (σ) describes how easily electric charges can move through a material. It is the reciprocal of resistivity (ρ):

σ=1ρσ = \frac{1}{ρ}σ=ρ1

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  High conductivity materials: Metals such as silver, copper, and gold are excellent conductors because they have free-moving electrons. For instance, silver has the highest conductivity among metals.

  
  


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  Low conductivity materials: Insulators such as rubber, glass, and plastic have very low conductivity because they lack free electrons.

  
  


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  Moderate conductivity: Semiconductors like silicon and germanium have conductivity that can be controlled by doping and temperature.

  
  

The SI unit, Siemens per meter (S/m), is dimensionally expressed as:

[S/m]=[Ω−1⋅m−1][S/m] = [Ω^{-1}·m^{-1}][S/m]=[Ω−1⋅m−1]

This means conductivity measures how many amperes of current will flow when a unit voltage is applied across a material of a specific length and cross-sectional area.

Examples in daily life:

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  Copper wires are widely used in electrical circuits due to their high conductivity.

  
  


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  Pure water is a poor conductor, but when salts are dissolved, its conductivity increases significantly.

  
  


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  Semiconductors form the backbone of modern electronics because their conductivity can be tuned.

  
  

Understanding conductivity is crucial in electrical engineering, material science, and physics, as it determines how effectively a material can carry current.