NDA General Ability Question (2025) — Solution

Step-by-step solution

For a very long current-carrying solenoid, the magnetic field at any point well inside it is given by B = _0 n I, where _0 is the permeability of free space, n is the number of turns per unit length, and I is the steady current. Since the parameters n and I are constant, the magnetic field has a constant magnitude. Furthermore, the direction of the magnetic field is parallel to the axis of the solenoid throughout its interior. Therefore, the magnetic field inside a very long solenoid is uniform.