NEET UG PHYSICS MCQ: MAGNETISM AND MATTER

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The effective length of a magnet is 31.4 cm and its pole strength is 0.5 Am. Calculate its magnetic moment. If it is bent in form of semicircle, then magnetic moment will be

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Correct option: A

0.157\mathrm{\;A}{\mathrm{m}^2},\mathrm{\;}0.01\mathrm{\;A}{\mathrm{m}^2}

Option A (

0.157\mathrm{\;A}{\mathrm{m}^2},\mathrm{\;}0.01\mathrm{\;A}{\mathrm{m}^2}

) is correct because the magnetic moment is calculated as

M = m \times l

initially and then

M' = m \times (2r)

where

r = l/\pi

when bent into a semicircle.

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. Then magnetic flux linked with the coil is [Wb] The area of hysteresis loop of a material is equivalent to

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7.5\;gm/c{m^3}

) A bar magnet of moment

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. The torque acting on the magnet is Assertion(A): Earth's magnetic field inside a closed iron box is less as compared to the out side.

Reason(R): The magnetic permeability of iron is low.