JEE Main2014PhysicsMagnetic Properties of MatterActual
The magnetic field of earth at the equator is approximately 4 × 1 0 - 5 T . The radius of earth is 6.4 × 1 0 6 m . Then the dipole moment of the earth will be nearly of the order of :
Options
- A10 20 A m 2
- B10 16 A m 2
- C10 10 A m 2
- D10 23 A m 2
Correct answer
D. 10 23 A m 2
Step-by-step solution
B = μ 0 4 π · M d 3 = 1 0 - 7 × M 6.4 × 1 0 6 3 ∴    4 × 1 0 - 5 = 1 0 - 7 × M 6.4 × 1 0 6 3 ∴    M = 6.4 × 1 0 6 3 × 4 × 1 0 - 5 1 0 - 7 = 6.4 3 × 1 0 1 8 × 4 × 1 0 2 = 6.4 3 × 4 × 1 0 2 0 = 1 . 0 4 8 × 1 0 2 3 ≈ 10 23   A m 2