4.9
19.4
9.7
14.6
Magnetic field due to bar magnet of pole strength of m is given as at equatorial position is given as
B = μ₀/4π * (m/r³)
where r is the distance from the center of the magnet.
At neutral points, the magnetic field due to the bar magnet is equal and opposite to the horizontal component of the Earth's magnetic field.
Therefore,
B = BH
μ₀/4π * (m/r³) = BH
10⁻⁷ * (m/(0.3)³) = 3.6 × 10⁻⁵
m = 3.6 × 10⁻⁵ * (0.3)³ / 10⁻⁷
m = 3.6 × 10⁻⁵ * 0.027 / 10⁻⁷
m = 9.72 × 10⁻³ / 10⁻⁷
m = 9.72 × 10⁴ Am²
m ≈ 9.7 Am²
Therefore, the magnetic moment of the magnet is approximately 9.7 Am².