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| Numerical - 01 |
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| 01. A short bar magnet placed with its axis at 300 with a uniform external magnetic field of 0.16 T experiences a torque of magnitude 0.032 J. |
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| (a) Estimate the magnetic moment of the magnet. |
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| (b) If the bar were free to rotate, which orientation would correspond to its (i) stable, and (ii) unstable equilibrium? What is its potential energy in the field for cases (i) and (ii)? |
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| Suggested solution: |
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| (b) Potential energy of a magnetic dipole in an external magnetic field |
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| In this case, the potential energy is minimum and is given by |
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(ii) The bar is in in unstable
equilibrium when
 is
antiparallel to
 i.e.,
when q = 180o. In this case, the
potential is maximum and is given by U = +MB = +0.064J. |
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