Q3 of 44 Page 200

A short bar magnet placed with its axis at 30° with a uniform external magnetic field of 0.25 T experiences a torque of magnitude equal to 4.5 × 10–2 J. What is the magnitude of magnetic moment of the magnet?

Given:


Angle between axis of bar magnet and external magnetic field, θ = 30°


Strength of external magnetic field, B = 0.25 T


Torque experienced by bar magnet, Τ = 4.5 × 10-2J



We know that, when a Bar magnet is placed in a uniform magnetic field it experiences a Net torque given by,


T = M × B …(1)


T = M × B × Sinθ


Where,


M = magnetic moment


T = Torque on bar magnet


θ = angle between magnetic field and magnetic moment


From equation (1) we can write,




M = 0.36 JT-1


Hence, the magnitude of moment of the Bar magnet is 0.36JT-1.


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