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JEE Main20204 Sep 2020Evening ShiftPhysicsMagnetic Effects of CurrentActual

A circular coil has moment of inertia 0 . 8 kg m 2 around any diameter and is carrying current to produce a magnetic moment of 20 Am 2 . The coil is kept initially in a vertical position and it can rotate freely around a horizontal diameter. When a uniform magnetic field of 4 T is applied along the vertical, it starts rotating around its horizontal diameter. The angular speed the coil acquires after rotating by 60 o

Options

  1. A10   rad   s - 1
  2. B10 π  rad  s - 1
  3. C20 π  rad  s - 1
  4. D20   rad   s - 1

Correct answer

A. 10   rad   s - 1

Step-by-step solution

From energy conservation 1 2 Iω 2 = U n - U t = - MBcos 60 ° - ( - MB ) MB 2 = 1 2 Iω 2 20 × 4 2 = 1 2 ( 08 ) m 2 100 = ω 2 ω = 10 rad

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