A solenoid with 1000 turns per meter carries \( 1.5 \, \text{A} \). What is the magnetic field inside? (\( \mu_0 = 4 \pi
**Field outside long solenoid** considered negligible because magnetic lines are concentrated inside and return path spreads over large area outside, making B_out ≈ 0. This justifies using solenoid for uniform field experiments, with n = 950 m⁻¹, I = 1.4 A giving B = 4π×10⁻⁷×950×1.4 = 1.67×10⁻³ T. B = μ₀ n I . B = 4 π × 10⁻⁷ × 1000 × 1.5 = 6 π × 10⁻⁴ ≈ 1.885 × 10⁻³ T . Using F = q v B sinθ, F = I l B sinθ, B = μ₀ I/(2π r), B = μ₀ N I/(2R) and τ = N I A B
Ref: NCERT > Physics Book > Moving Charge and Magnetism > Solenoid, Toroid and Ampere's Law
