Question

The S.I. unit of specific resistance is
$A.$ $ohm{\text{ m}}$
$B.$ $ohm$ ${m^{ - 1}}$
$C.$ $ohm{\text{ }}{{\text{m}}^2}$
$D.{\text{ }}{\left( {ohm} \right)^{ - 1}}$

Answer 1

Hint – Here we will proceed by writing the formula for specific resistance after that we can easily find out the unit of specific resistance.

Complete step by step answer:
Specific resistance is defined as the resistance offered per unit length and unit cross-sectional area when a known amount of voltage is applied.
The mathematical representation is as follows:
$\rho = \dfrac{{RA}}{L}$
Where,
$\rho = $ specific resistance
$R = $ resistance
$A = $ cross-sectional area
$L = $ length of the material
Specific resistance is the reciprocal of specific conductance, which is defined as a measure of material’s ability to conduct electricity. The symbol representation of specific resistance is $\kappa $.
Unit of specific resistance:
S.I. a unit of specific resistance is ohm $ \times $ meter which is expressed as ohmmeter $\left( {\Omega m} \right)$.
Therefore, the correct option is A.
An ohmmeter is an electrical instrument that measures electrical resistance. Micro-ohmmeters make low resistance measurements. Megohmmeters measure large values of resistance.

Note – Whenever we come up with this type of problem where we are asked to find the unit of any quantity. Then we first write the formula to calculate the unit and after solving that we will get the required S.I. unit asked for that quantity (here specific resistance).