Question

Which of the following is NOT the reason behind selecting marble for making 'formers' for inductance coils?
1. It is comparatively cheap.
2. It is a non-magnetic material.
3. It can be easily machined. 
4. It has a very small co-efficient of thermal expansion.

Answer 1

Correct Answer - Option 4 : It has a very small co-efficient of thermal expansion.

Criteria for selecting marble for making 'formers' for inductance coils:

• It is a non-magnetic material.
• It is comparatively cheap.
• It can be easily machined. 
• Increased mechanical resistance
• Higher resistance for high temperatures
• Better electrical isolation

 

'It has a very small co-efficient of thermal expansion' is NOT the reason behind selecting marble for making 'formers' for inductance coils.