A bar magnet has pole strength m, magnetic length 2l and magnetic moment M. It is cut into two equal pieces by a plane perpendicular to its magnetic axis. For each resulting magnet, pole strength m′ and magnetic moment M′ are:
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Question

A bar magnet has pole strength m, magnetic length 2l and magnetic moment M. It is cut into two equal pieces by a plane perpendicular to its magnetic axis. For each resulting magnet, pole strength m′ and magnetic moment M′ are:

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G1 Physics · Accepted Answer

For a transverse cut (plane perpendicular to the magnetic axis), the cross-sectional area of each piece remains unchanged. Therefore pole strength remains unchanged: m′ = m. The magnetic length becomes half: 2l′ = l. Original magnetic moment: M = m(2l). For each piece, M′ = m·l = M/2. Hence, m′ = m, M′ = M/2.