Question

Alloys like manganin and constantan are used for making standard resistance coils as they have________.

Answer 1

Alloys are combinations of metals or metals and other elements. Certain other metals/elements can be added to the metals in specific ratios to form alloys to confer certain properties to metals or strengthen some of their present properties.

The properties of an alloy are different from the properties of the constituent metals:

1. Alloys are stronger than the metals from which they are made.
2. Alloys are harder than their constituent metals.
3. Alloys are more resistant to corrosion.
4. Alloys have lower melting points than constituent metals.
5. Alloys have lower electrical conductivity than pure metals.

• Manganin is an alloy of copper (Cu), nickel (Ni), and manganese (Mn)
• Constantan is an alloy of copper (Cu) and nickel (Ni).
• Alloys like manganin and constantan are used for making standard resistance coils as they have high resistivity and a low-temperature coefficient of resistance.
• Therefore, these alloys are used for making wire-bound standard resistors. Their resistance value would change very little with temperature.
• In alloys, like constantan, atoms are in disorder so alloys have high resistivity.
• Their additional disorder due to temperature increase is insignificant. That is why alloys have no temperature dependence of resistivity.

Thus, alloys like manganin and constantan are used for making standard resistance coils as they have high resistivity.