NEET 2020 · PhysicsSolenoid fieldPrevious Year Question
A long solenoid of 50 cm length having 100 turns carries a current 2.5 A. The magnetic field at the centre of the solenoid is (μ₀ = 4π × 10⁻⁷ T m A⁻¹)
Answer: (C) 6.28 × 10⁻⁴ T. Answer: (C) Solution: For a long solenoid, B = μ₀ n I, where n = N/L is turns per metre.
- A.6.28 × 10⁻⁵ T
- B.3.14 × 10⁻⁵ T
- C.6.28 × 10⁻⁴ T✓
- D.3.14 × 10⁻⁴ T
Correct Answer
(C) 6.28 × 10⁻⁴ T
Solution & Explanation
Answer: (C) Solution: For a long solenoid, B = μ₀ n I, where n = N/L is turns per metre. n = 100 / 0.50 = 200 turns m⁻¹. B = (4π × 10⁻⁷) × 200 × 2.5. B = 4π × 10⁻⁷ × 500 = 2000π × 10⁻⁷. B ≈ 6.28 × 10⁻⁴ T.
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