The alloys constantan and manganin are used to make standard resistance due to they have?

Constantan and manganin are used to make standard resistances because of their very stable and temperature-independent resistances.

Temperature Coefficient of Resistance: Both constantan and manganin have a very low temperature coefficient of resistance. This means that their resistance does not change significantly with temperature. As a result, these materials provide more accurate and stable measurements over a wide range of temperatures.

Alloy Composition: Constantan is an alloy made primarily of copper and nickel, while manganin is made of copper, manganese, and nickel. The specific composition of these alloys ensures that they maintain their resistance even under varying environmental conditions.

Precision in Measurement: Since resistors made from constantan and manganin are stable, they are used in high-precision applications like standard resistors in laboratories and calibration instruments.

In summary, constantan and manganin are used to make standard resistances because they have low temperature coefficients of resistance, ensuring stable and reliable measurements.