To protect the instrument from magnetic field, it is completely surrounded by (a) soft ferromagnetic substance. (b) diamagnetic substance only. (c) paramagnetic substance only. (d) both diamagnetic and paramagnetic substances.

Answer: (a). A soft ferromagnetic material has very high permeability, so field lines crowd into the shell and pass around the inside. The space enclosed by the shell is left almost field free. Dia- and paramagnets have μr ≈ 1, so they cannot do this. So the answer is (a) soft ferromagnetic substance.

To protect the instrument from magnetic field, it is completely… | MHT CET 2025 (25 Apr, Shift 2)

Q3MHT CET 2025 · 25 APR · SHIFT 2Easy

Hysteresis, Soft Iron vs Steel & Shielding

To protect the instrument from magnetic field, it is completely surrounded by

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Answer: (a)

A soft ferromagnetic material has very high permeability, so field lines crowd into the shell and pass around the inside.
The space enclosed by the shell is left almost field free. Dia- and paramagnets have $\mu_r \approx 1$ , so they cannot do this.
So the answer is (a) soft ferromagnetic substance.

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