Why is manganin used for making standard resistors?

QUESTION:

Why is manganin used for making standard resistors?

ANSWER:

For standard resistors, resistance should be a constant value at different temperatures. In case of Manganin temperature coefficient of resistance is very less. So its resistance is almost constant over a wide range of temperature. Due to this reason Manganin is used to prepare standards resistances.

Note:

Temperature coefficient of resistance α is the ratio between change in resistance per unit resistance and per unit change in temperature.

α = (R2 – R1)/R1 (t2-t1)