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Units And Measurement

Question
CBSEENPH11020665

A rectangular coil of length 0.12 m and width 0.1 m having turns of wire is suspended vertically in a uniform magnetic field of strength 0.2 Wb/m2.The coil carries a current of 2 A. If the plane of the coil is inclined at an angle of 30o with the direction of the field, the torque required to keep the coil in stable equilibrium will be

  • 0.15 Nm

  • 0.20 Nm

  • 0.24 Nm

  • 0.12 Nm

Solution

B.

0.20 Nm

Given N = 50
B = 0.2 Wb/m2, I = 2A
θ = 60o, A = 0.12 x 0.1 = 0.012 m2

Thus, torque required to keep the coil in stable equilibrium i.e.,
\tau  = NIAB sin θ = 50 x 2 x 0.012 x0.2 sin 60o
50 space straight x space 20 space straight x space 0.12 space space straight x space 0.2 space straight x space fraction numerator square root of 3 over denominator 2 end fraction space equals space 0.20 space Nm