Question

For industrial furnaces where temperature should remain constant, which material is suitable for heating element?
1. Nichrome
2. Eureka
3. Tungsten
4. Platinum

Answer 1

Correct Answer - Option 1 : Nichrome

Nichrome:

Composition: 80% of Ni and 20% of Cr

Properties of Nichrome:

• Resistivity: 40 µΩ cm
• Temperature coefficient of resistance: 0.0004 / ⁰C
• Melting point: 1400 ⁰C
• Specific gravity: 8.4gm /cm³
• High resistance to oxidation
   

Application:

• Used in making heating elements for electric heaters and furnaces.
   

Important Points

• Nichrome is the best suitable and ideal material for making heating elements.
• It is having comparatively high resistance.
• When the heating element is heated the first time, chromium of alloy reacts with oxygen of atmosphere and forms a layer of chromium oxide on the outer surface of the heating element. This layer of chromium oxide works as a protective layer for element and protect the material beneath these layers against oxidation, preventing the element wire from breaking and burning out.
• Heating elements made of Nichrome can be used for continuous operation at a temperature up to 1200 ⁰C.