Question

Magnets cannot be made from which of the following substances?

• A. all of the above
• B. Copper
• C. Nickel
• D. Iron

Answer 1

The correct option is B

Copper

Explanation :

• Materials having high susceptibility , high permeability , high retentivity and high coercivity are suitable for making permanent magnets.
• High susceptibility ensures strong magnetisation of the material and high permeability ensures that magnetic field can pass through the material strongly.
• High retentivity ensures that the material retains its magnetic property strongly even in absence of external magnetising field and high coercivity ensures that the material doesn’t get demagnetised in presence of opposite external field .
• Ferromagnetic substances possess the above properties , hence they are suitable for making magnets .
• Iron and nickel are ferromagnetic whereas copper is diamagnetic in nature.

Therefore , Magnets are not made up of copper.

Hence, Correct option is (C).

Additional information :
Diamagnetic substances have small and $-ve$ magnetic susceptibility so they get feebly magnetised in the direction opposite to the applied magnetising field .