A 250 -Turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 μA and subjected to…

A 250-Turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 μA and subjected to a magnetic field of strength 0.85 T. Work done for rotating the coil by 180° against the torque is:
  1. 9.1 μJ
  2. 4.55 μJ
  3. 2.3 μJ
  4. 1.15 μJ

Solution

W=MB cosθ1-cosθ2
When it is rotated by angle 180o then θ1=0° and θ2=180°
W=2MB
W=2NIAB
=2×250×85×10-6 1.25×2.1×10-4×85×10-2
=9.1 μJ

Asked in: NEET 2017

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