JEE Main20204 Sep 2020Evening ShiftPhysicsMagnetic Properties of MatterActual
A paramagnetic sample shows a net magnetisation of 6 A / m when it is placed in an external magnetic field of 0 . 4 T at a temperature of 4 K . When the sample is placed in an external magnetic field of 0 . 3 T at a temperature of 24 K , then the magnetisation will be :
Options
- A1   A / m
- B4   A / m
- C2 . 25   A / m
- D0 . 75   A / m
Correct answer
D. 0 . 75   A / m
Step-by-step solution
According to Curie's Law, χ ∝ 1 T Therefore, χ 1 T 1 = χ 2 T 2 Also, χ = M B So, M 1 T 1 B 1 = M 2 T 2 B 2 On substituting the values, 6 × 4 0 . 4 = M 2 × 24 0 . 3 Therefore, M 2 = 0 . 75   A   m - 1