Question

Mark the correct reasons/s why nichrome is used for making heating element of electrical appliances
A. Nichrome does not oxidise
B. Nichrome doesn’t burn easily at high temperatures as it has higher melting and boiling point than metals
C. Nichrome has higher resistivity and consequently a higher resistance
D. All

Answer 1

Hint: Nichrome is an alloy that conducts electricity although it has high resistivity, due to this property it is used for making heating elements of electrical appliances.

Step by step answer:
Nichrome alloy is a mixture of two elements- 80% Nickel and 20% Chromium. Nichrome does not oxidise in air or burn easily like other metals when heated at high temperature. Also, it has very high melting and boiling points, so it does not melt or break easily when a large amount of current flows through it whereas other metals like copper and aluminium do. It can easily remain in a red hot state for a long time without getting melted or burnt.

Fig: Resistivity vs Temperature graph for Nichrome

Even at 0 K temperature the specific resistivity of Nichrome is very high and it varies linearly with increase in temperature. It has a high specific resistivity due to which it opposes the flow of current and hence it has a high resistance too. It is also very ductile so it can easily be drawn into thin wires. Due to all these properties it is the most suitable material for making heating elements in electric heaters, electric rods, electric iron etc.

The correct answer is D. All

Note: The working of heating elements used in electrical appliances is based on the fact that when current is passed through a resistance heat is produced and this is known as the heating effect of electric current.