The magnetic field inside a current carrying very long solenoid is

The magnetic field inside a current-carrying very long (ideal) solenoid is uniform. This means the field has a constant magnitude and direction at all points within the interior region. According to Ampere's Law, for a sufficiently long and densely wound coil, the magnetic field lines inside are parallel to the solenoid's axis and are represented as straight lines [1]. This parallel arrangement indicates that the magnetic field strength is the same at all points inside the solenoid. While the field may diverge or weaken near the ends of a finite solenoid, in the case of a 'very long' or infinite solenoid, the internal field is homogeneous and the external field is considered approximately zero [1]. The magnitude of this uniform field is given by the formula B = μ₀nI, where 'n' is the number of turns per unit length.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > 12.2.3 Magnetic Field due to a Current through a Circular Loop > p. 200