The magnetic field lines inside a solenoid are nearly parallel because:
**Core magnetization** M = (μ_r -1)nI, so B = μ₀(nI + M). High μ_r materials like soft iron increase B dramatically for same nI, used in electromagnets, with μ_r up to 5000, enabling strong fields with low current. Inside a solenoid, the magnetic field lines are nearly parallel due to the uniform distribution of current loops along its length, creating a consistent field direction and magnitude, especially in a long solenoid where end effects are minimal. Substituting values gives The current loops produce a uniform field, which matches expected magnitude for this magnetic configuration, confi
Ref: NCERT > Physics Book > Magnetism and Matter > Solenoid with Magnetic Core and Magnetic Properties
