A short bar magnet placed with its axis at $3 0^{o}$ with a uniform external magnetic field of 0.25 T experiences a torque of magnitude equal to $4.5 \times 1 0^{- 2}$ J. What is the magnitude of magnetic moment of the magnet?

Question

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Answer 1

Given data
angle between magnetic moment and magnetic field $θ = 3 0^{0}$
External magetic field $B = 0.25 T$
Torque $τ = 4.5 \times 1 0^{- 2} J$
The torque experienced by a bar magnet placed at an angle $θ$ with the external magnetic field $B$ is given by
$τ = M B sin θ$
$⟹ 4.5 \times 1 0^{- 2} = M \times 0.25 s i n 3 0^{\circ}$
$⟹ M = 0.36 J T^{- 1}$

Answer 2

Given data

angle between magnetic moment and magnetic field

θ = 3 0^{0}

External magetic field

B = 0.25 T

Torque

τ = 4.5 \times 1 0^{- 2} J

The torque experienced by a bar magnet placed at an angle

θ

with the external magnetic field

B

is given by

τ = M B sin θ

⟹ 4.5 \times 1 0^{- 2} = M \times 0.25 s i n 3 0^{\circ}

⟹ M = 0.36 J T^{- 1}