NEET 2019 · PhysicsFaraday lawPrevious Year Question
A 800 turn coil of effective area 0.05 m² is kept perpendicular to a magnetic field 5 × 10⁻⁵ T. When the plane of the coil is rotated by 90 degrees around any of its coplanar axis in 0.1 s, the emf induced in the coil will be:
Answer: (D) 0.02 V. Answer: (d) Solution: Initially the coil's plane is perpendicular to B, so flux is maximum: Φ_i = NBA.
- A.2 V
- B.0.2 V
- C.2 × 10⁻³ V
- D.0.02 V✓
Correct Answer
(D) 0.02 V
Solution & Explanation
Answer: (d) Solution: Initially the coil's plane is perpendicular to B, so flux is maximum: Φ_i = NBA. After a 90° rotation the plane becomes parallel to B, so Φ_f = 0. Average emf = |ΔΦ|/Δt = NBA/Δt = (800 × 5 × 10⁻⁵ × 0.05) / 0.1. = (2 × 10⁻³) / 0.1 = 0.02 V. So the answer is D (0.02 V).
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