A compass needle behaves as a magnetic dipole of moment

PHYSICS · Subjective · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Magnetostatics · Magnetostatics

The Boundary-Value Problem, Ch The magnetic multipole expansion and the magnetic scalar potential

Problem

A compass needle behaves as a magnetic dipole of moment m=0.15 A m2m = 0.15\,\mathrm{A\,m^2}. It sits in a local horizontal magnetic field of magnitude B=5.0×10−5 TB = 5.0\times10^{-5}\,\mathrm{T}, held at rest with its moment at 30∘30^\circ to the field direction. Find the magnitude of the torque on the needle at this instant.

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