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A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is: (μ₀ = 4π × 10⁻⁷ T m A⁻¹)
- 3.14 × 10⁻⁴ T
- 6.28 × 10⁻⁵ T
- 3.14 × 10⁻⁵ T
- 6.28 × 10⁻⁴ T
Correct answer: 3.14 × 10⁻⁴ T
Solution
The magnetic field inside a solenoid is given by B = μ₀ * n * I, where n = N/L is the number of turns per unit length. Here, N = 100, L = 0.5 m, and I = 2.5 A. Substituting, n = 100/0.5 = 200 turns/m. Thus, B = (4π × 10⁻⁷) * 200 * 2.5 = 3.14 × 10⁻⁴ T.
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