A bar magnet of magnetic moment M is aligned parallel to the direction of a uniform magnetic field B. Calculate work done to align the magnetic moment (i) opposite to the field (ii) normal to field direction?

A bar magnet of magnetic moment M is aligned parallel to the direction

1.	A bar magnet of magnetic moment M is aligned parallel to the direction of a uniform magnetic field B. Calculate work done to align the magnetic moment (i) opposite to the field (ii) normal to field direction?
Answer» Work done in turning a dipole from orientation `theta_1` to `theta_2` is given by `W=-MB(cos theta_2-cos theta_1)` (i) In aligning `vecM` opposite to magnetic field, `theta_1=0`, `theta_2=180^@` `:. W=-MB ( cos 180^@-cos 0^@)` `=-MB(-1-1)=2MB` (ii) In aligning `vecM` perpendicular to magnetic field, `theta_1=0^@`, `theta_2=90^@` `W=-MB(cos 90^@-cos0^@)=+MB`

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A bar magnet of magnetic moment M is aligned parallel to the direction of a uniform magnetic field B. Calculate work done to align the magnetic moment (i) opposite to the field (ii) normal to field direction?

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