The correct option is Uniform.
Explanation
A solenoid is a long coil of wire consisting of many circular turns wrapped in the shape of a cylinder. When an electric current flows through it, it generates a magnetic field similar to that of a bar magnet.
Analysis of Magnetic Field Lines:
- The magnetic field lines inside a long current-carrying solenoid are parallel straight lines.
- In physics, parallel and equidistant magnetic field lines indicate that the magnetic field strength and direction are constant at every point within that region.
- Therefore, the magnetic field inside the solenoid is uniform.
- In contrast, the field outside the solenoid is non-uniform and weak (approaching zero for an ideal, infinitely long solenoid).
Key Takeaway: The magnetic field inside a long current-carrying solenoid is uniform, represented by parallel straight lines along the axis of the coil.