Question

Why are alloys used for making standard resistance coils?

Answer 1

Resistance coils:

1. A coil of wire that offers electrical resistance to the passage of a current and dissipates heat to the surroundings is a resistance coil. They are used in the design of heating elements like electric cookers, iron boxes, electric toasters, electric water heaters, etc.

1. Resistors offer opposition to the flow of current. Hence, the electric energy is dissipated in the form of heat.
2. Resistance coils are used to produce the heating effect of the current, hence they need the material of high resistance and low-temperature sensitivity.
3. Alloys have a high resistivity and a very small temperature coefficient (temperature sensitivity). Hence, they are used for making standard resistance.
4. Alloys like manganin, nichrome, etc. are used in the manufacture of resistors, particularly ammeter shunts, because of their virtually zero temperature coefficient of resistance and long-term stability.
5. Standard resistance coils are made from alloys like manganin and constantan because of their essentially temperature-independent properties.

Hence, standard resistance coils are made from alloys like manganin and constantan because of their high resistivity and low-temperature coefficient of resistance.