Physics

Problem

A compass needle initially at

20^{\circ}

to a uniform magnetic field experiences an initial angular acceleration

\alpha_{0}

. If the magnitude of the external magnetic field is suddenly doubled while the needle’s moment of inertia and magnetic moment remain unchanged, which statement best describes the needle’s new initial angular acceleration

\alpha_{\text{new}}

? a)

\alpha_{\text{new}} = \sqrt{2}\,\alpha_{0}

\alpha_{\text{new}} = 2\alpha_{0}

\alpha_{\text{new}} = 4\alpha_{0}

\alpha_{\text{new}} = \dfrac{1}{2}\alpha_{0}

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