Question

The units of conductivity are:
A. $Siemen{{s}^{-1}}c{{m}^{-1}}$
B. $Siemens\,cm$
C. $Siemens\,c{{m}^{-1}}$
D. $Siemens\,c{{m}^{-1}}\,mol{{e}^{-1}}$

Answer 1

Hint: Conductivity is the measure of the ease at which an electric charge or heat can pass through a material. A conductor is a material which gives very little resistance to the flow of an electric current or thermal energy.

Complete step by step answer:
Materials are classified as metals, semiconductors, and insulators. Metals are good conductors whereas non metals are bad conductors. The conductivity of the semiconductors lies between that of metals and non metals.
We will derive the formula of conductivity and from there we will get the unit of conductivity.
Conductivity is the reciprocal of resistivity.
$\sigma \,=\,\dfrac{1}{\rho }$
$R\,=\,\rho \dfrac{l}{A}$ , where R = resistance, l = length, A = area
Therefore expression of conductivity will be as follows.
$\sigma \,=\,\dfrac{l}{AR}$
The unit for the reciprocal of resistance is $siemens$.
Unit of conductivity = $\dfrac{cm}{c{{m}^{2}}}\,siemens$
= $siemen\,c{{m}^{-1}}$

So, the correct answer is Option C.

Note: Both resistance and resistivity describe how difficult it is to form electrical current flow through a material, but unlike resistance, resistivity is an intrinsic property. This suggests that each one of pure copper wires (which haven't been subjected to distortion of their crystalline structure etc.), regardless of their shape and size, have an equivalent resistivity, but a long, thin copper wire incorporates a much larger resistance than a thick, short copper wire.
Every material has its own characteristic resistivity. For instance, rubber has a far larger resistivity than copper. Electric current consists of a flow of electrons. In metals there are many electron energy levels near the Fermi level, so there are many electrons available to move. This is often what causes the high electronic conductivity of metals.