A straight rigid copper bar of length carries a steady current of along

PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Magnetostatics · Magnetostatics

Electricity, Magnetism and Electromagnetism, Ch The Biot-Savart law and the fields of steady currents

Problem

A straight rigid copper bar of length

0.80\,\mathrm{m}

carries a steady current of

12\,\mathrm{A}

along

+\hat{\mathbf{x}}

. It lies in a uniform magnetic field of magnitude

0.25\,\mathrm{T}

whose direction lies in the

xy

-plane at

40^\circ

from

+\hat{\mathbf{x}}

, that is

\mathbf{B} = 0.25(\cos 40^\circ\,\hat{\mathbf{x}} + \sin 40^\circ\,\hat{\mathbf{y}})\,\mathrm{T}

. The field the bar's own current makes is negligible, and gravity is ignored. ((a)) Find the magnitude of the magnetic force on the bar and state its direction. ((b)) In the same field a rigid square coil of

60

turns, of side

2.5\,\mathrm{cm}

, carries

12\,\mathrm{A}

and has its magnetic moment along

+\hat{\mathbf{z}}

. Find the magnitude of the torque on the coil.

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