Question

When a ferromagnetic material is heated to temperature above its curie point, thematerial :

• A. is permanently magnetized
• B. remains ferromagnetic
• C. behaves like a diamagnetic material
• D. behaves like a paramagnetic material

Answer 1

Answer: (D)

Ferromagnetism decreases with rise in temperature
Ferromagnetic substances are strongly attracted by a magnet, show all properties of a paramagnetic substance to a much higher degree. While paramagnetic substances are feebly attracted by a magnet. When ferromagnetic substance is heated, then at a definite temperature the ferromagnetic property of the substance suddenly disappears and the substance becomes paramagnetic. The temperature above which a ferromagnetic substance becomes paramagnetic is called the curie temperature (point) of the substance.
The susceptibility of a paramagnetic substance varies inversely as the Kelvin temperature of the substance, that is
${\chi }_m\propto \frac{1}{T}$
This is known as Curie’s law.