What is the magnitude of the equatorial magnetic field due to a bar magnet of length 5.0 cm and having magnetic dipole moment 0.40 A m² at a distance of 50 cm from its mid point ?

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Accepted Answer

(4) 3.2×10⁻⁷ T. Given: m=0.40 A m², r=50 cm=0.50 m, magnet length 5.0 cm. Idea: r is ten times the magnet's length, so the short-dipole result applies: B_E=(μ₀)/(4π)m/(r³) with (μ₀)/(4π)=10⁻⁷ T m A⁻¹. r³=(0.50)³=0.125 m³. B_E=((10⁻⁷)(0.40))/(0.125)=3.2×10⁻⁷ T. On the equatorial line this field points antiparallel to the magnet's moment; on the axis at the same distance it would be twice as large. So the equatorial field is 3.2×10⁻⁷ T.

What is the magnitude of the equatorial magnetic field due to a bar magnet of length 5.0 cm and having magnetic dipole moment 0.40 A m² at a distance of 50 cm from its mid point ?

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