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AP EAMCET · PHYSICS · Magnetic Properties of Matter

At a place the horizontal component of earth's magnetic field is \(3 \times 10^{-5} \mathrm{~T}\) and the magnetic declination is \(30^{\circ}\). A compass needle of magnetic moment \(18 \mathrm{Am}^2\) pointing towards geographic north at this place experiences a torque of

  1. A \(36 \times 10^{-5} \mathrm{Nm}\)
  2. B \(18 \times 10^{-5} \mathrm{Nm}\)
  3. C \(54 \times 10^{-5} \mathrm{Nm}\)
  4. D \(27 \times 10^{-5} \mathrm{Nm}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(27 \times 10^{-5} \mathrm{Nm}\)

Step-by-step Solution

Detailed explanation

\(\mathrm{B}_{\mathrm{H}}=3 \times 10^{-5} \mathrm{~T}, \phi=30^{\circ}, \mathrm{M}=18 \mathrm{Am}^2\) Torque, \(\tau=\mathrm{MB}_{\mathrm{H}} \sin \phi=18 \times 3 \times 10^{-5} \sin 30^{\circ}\) \(=27 \times 10^{-5} \mathrm{Nm}\)
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