Question:
A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field \(\vec{B}\). Then the field inside the paramagnetic substance is :
A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field \(\vec{B}\). Then the field inside the paramagnetic substance is :
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A perfectly diamagnetic body (\(\chi = -1\), \(\mu_r = 0\)) expels the field completely from itself and from any cavity it encloses.
Updated On: Nov 5, 2026
- \(\vec{B}\)
- zero
- much large than \(|\vec{B}|\) and parallel to \(\vec{B}\)
- much large than \(|\vec{B}|\) but opposite to \(\vec{B}\)
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The Correct Option is B
Solution and Explanation
A perfectly diamagnetic material has susceptibility \(\chi = -1\), so \(\mu_r = 1 + \chi = 0\) and the magnetic field inside the material is zero (field lines are completely expelled).
The material of the sphere forms a closed shell around the cavity. The external field cannot penetrate the shell, so the net field in the cavity is also zero.
Hence the field inside the paramagnetic substance at P is zero, irrespective of its (small) paramagnetism.
Answer: (2) zero
The material of the sphere forms a closed shell around the cavity. The external field cannot penetrate the shell, so the net field in the cavity is also zero.
Hence the field inside the paramagnetic substance at P is zero, irrespective of its (small) paramagnetism.
Answer: (2) zero
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