Question

Curie-Weiss law is obeyed by iron

• A. at Curie temperature only
• B. at all temperatures
• C. below Curie temperature
• D. above Curie temperature

Answer 1

Answer: (D)

above Curie temperature

Answer 2

Iron is a ferromagnetic substance. The Curie point for iron is $1043\, K \left(=770^{\circ} C \right)$. If the temperature of a ferromagnetic material is raised above a certain critical value called the Curie temperature the exchange coupling ceases to be effective. Most such materials then become paramagnetic. Also after Curie point, susceptibility of a ferromagnetic substance varies inversely with its absolute temperature. Hence, a ferromagnetic substance obeys Curie-Weiss law above its Curie temperature.