Question

S.I. unit of electrical conductivity is:
(A) Siemen
(B) Siemen/meter
(C) Siemen meter
(D) ohm metre

Answer 1

Hint
For solving this question we have to know about conductivity i.e., conductivity of any substance is the ability to allow electricity through ions. It can be of ionic, thermal or electrical. This unit measures the current flow through an electrolyte.

Complete step by step solution
First of all, it is necessary to know the specific resistance(resistivity).
Resistivity or a specific resistance of a material is a measure of the resistance, which it provides to the flow of current through it: specific resistance depends upon composition, temperature, pressure of the material. The reciprocal of resistivity is defined as specific conductance which is the ability to conduct electricity.
When electric current is passed through metallic rod of same cross-section then resistance of rod ($R$) is directly proportional to length of rod ($L$) and inversely proportional to the area of cross-section ($A$) of it.
$\Rightarrow$ $R \propto \dfrac{L}{A}$
$\Rightarrow$ $R = \rho \dfrac{L}{A}$
$\rho =$ it is a constant which is called specific resistance of conductor.$\mathop m\nolimits^2$This constant has different value for different materials as we know specific resistance is dependent on the physical properties of material like density and composition. For unit length and unit cross-sectional area, i.e., $L = 1cm$ and $\mathop {A = 1cm}\nolimits^2 ,\rho = r$
Specific resistivity is reciprocal to specific conduct $\sigma = \mathop {ohm}\nolimits^{ - 1} \times \dfrac{{cm}}{{\mathop {cm}\nolimits^2 }}$ $\Omega$which is donated by $\sigma$.
From the specific resistance formula,
$\rho = \dfrac{{unit{\text{ }}of{\text{ }}R \times unit{\text{ }}of{\text{ A}}}}{{unit{\text{ }}of{\text{ L}}}}$
When resistance $R$ is expressed in $\Omega$, area ($A$), and length ($L$) are in $m$.
Unit of specific conductance can be determined as we know conductivity is the reciprocal of resistivity so,
Unit of resistivity is $\mathop {ohm}\nolimits^{ - 1} \mathop m\nolimits^{ - 1}$.
So, the correct answer is option (B).

Note
IUPAC recommended resistivity term to specific resistance. Similarly, specific conductance is referred to its conductivity. So, the conductance of 1ml solution is called specific conductance. Conductance and conductivity are measured by determining the resistance and resistivity of electrolytic solution through a Wheatstone bridge filled in specific types of conductivity cells.