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# A Magnetised Needle of Magnetic Moment 4.8 × 10−2 Jt−1 is Placed at 30° with the Direction of Uniform Magnetic Field of Magnitude 3 × 10−2 T. Calculate the Torque Acting on the Needle. - Physics

ConceptTorque on Current Loop, Magnetic Dipole Torque on a Rectangular Current Loop in a Uniform Magnetic Field

#### Question

A magnetised needle of magnetic moment 4.8 × 10−2 JT−1 is placed at 30° with the direction of uniform magnetic field of magnitude 3 × 10−2 T. Calculate the torque acting on the needle.

#### Solution

The torque (τ) of a needle in uniform magnetic field will be given as

vectau = vecM xx vecB =MB sintheta

Here

M = magnetic moment = 4.8 ×10−2 J/T

B = magnetic field strength = 3 × 10−2 T

θ = angle with respect to field = 30°

So, the torque will be rewritten as

vectau= (4.8 ×10−2) × (3 × 10−2) sin 30°

or vectau = 14.4 xx 10^-4 xx 1/2 = 7.2 xx 10^-4 N

Is there an error in this question or solution?

#### APPEARS IN

Solution A Magnetised Needle of Magnetic Moment 4.8 × 10−2 Jt−1 is Placed at 30° with the Direction of Uniform Magnetic Field of Magnitude 3 × 10−2 T. Calculate the Torque Acting on the Needle. Concept: Torque on Current Loop, Magnetic Dipole - Torque on a Rectangular Current Loop in a Uniform Magnetic Field.
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