Question

Nichrome or Manganin is widely used in wire-bound standard resistors because of their.
(A) Temperature independent resistivity
(B) Very weak temperature-dependent resistivity
(C) Strong dependence of resistivity with temperature
(D) Mechanical strength

Answer 1

Hint We will first start with understanding the terms resistors and resistivity. Resistors are devices that are used in electrical circuits to control the electric current flowing through the circuits. Resistivity is a property of materials that shows the ability of the substance to conduct or resist the current flowing through it.

Complete step by step answer
The resistance of any material can be found to be directly proportional to the length of materials and inversely proportional to the cross-section area of the material. Hence it can be given as
$R \propto \dfrac{L}{A}$
$ \Rightarrow R = \rho \dfrac{L}{A}$
where $\rho $is the resistivity of the material and also proportionality constant
$\therefore \rho = R\dfrac{L}{A}$
The SI unit of resistivity is$\Omega m$.
We know that the Nichrome or Mangnin both materials are alloys. The resistivity of the Nichrome is in the range of ${10^{ - 4}}\Omega m$and for Manganin it is in the range of$44 \times {10^{ - 6}}\Omega m$. Nichrome and Mangnin are ohmic resistance which are the materials that obey the ohm's law. Ohm's law states that the electric current passing through any conductor is directly proportional to the potential difference at constant temperature and pressure.
A very prominent feature of ohmic resistance is that they are independent of temperature. The resistivity of such materials does not change more even when the temperature changes mean they are slightly independent of temperature means they possess very weak temperature dependence. As a result, they are widely used in the bound standard resistors.

Hence option (B) is the correct answer.

Note Resistance is the obstruction to the flow of electrons while resistivity is the characteristic property of a material. The former depends on the dimensions of the conductor while the latter only depends on the type of material and temperature to some extent.