A long solenoid has 1000 turns per metre and carries 2 A. The magnetic field strength inside is

1. Inside an ideal long solenoid: B = μ₀ n I. 2. Given n = 1000 turns/m, I = 2 A. 3. Substitute: B = μ₀ × 1000 × 2 = μ₀ × 2 × 10³. 4. Numerically: B = (4π × 10⁻⁷)(2 × 10³) ≈ 2.51 × 10⁻³ T. _Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", §4.8.1_