Multiple choice

A circular coil of radius 10 cm, 500 turns and resistance 2Ω is placed with its plane perpendicular to the horizontal component of the earth’s magnetic field. It is rotated about its vertical diameter through 180° in 0.25 s. Determine the magnitudes of the current induced in the coil, where the magnetic field at the place is 3.0 × 10–5 T.

  1. 0.94 × 10-3 A

  2. 1.9 × 10–3 A

  3. 0.471 × 10–3 A

  4. 0.3 × 10–3 A

  5. 0.6 × 10–3 A
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initial flux through the coil, Φ = BA cosθ = 3.0 × 10–5 × (π ×10–2) × cos 0º = 3π × 10–7 Wb. Final flux after the rotation, Φ= 3.0 × 10–5× (π×10–2) × cos 180° = –3π× 10–7 Wb. Therefore, estimated value of the induced emf is, ε= N ΔΦ / Δt= 500 × (6π× 10–7)/0.25 = 3.8 × 10–3VI = ε / R= 1.9 × 10–3 A

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