Why are alloys used for making standard resistance coils?

Explanation

For standard resistance coils, there should not be any variation in the value of resistance due to temperature changes because when current flows through a conductor, heat is generated and resistance of the conductor changes, which is not desirable. Alloys like nichrome and constantan are used for making standard resistance coils because of their low temperature coefficient of resistance. with the change in temperature, the resistance variation is very small which makes them suitable for this purpose. Also, these alloys have high resistivity which means that the size of a resistor is not much for a high value of resistance.