The magnetic field lines inside a current carrying long solenoid are in the form of

The magnetic field lines inside a current-carrying long solenoid are in the form of parallel straight lines. This pattern indicates that the magnetic field is uniform in both magnitude and direction throughout the interior of the solenoid. According to Ampere's Law, for an ideal or long solenoid, the field lines are directed parallel to the solenoid's central axis. These lines are densely packed and straight, reflecting a strong and constant internal field, whereas the field outside is nearly zero. This uniformity is a result of the superposition of magnetic fields from each individual turn of the coil, which cancel out in the radial direction and reinforce each other along the axis. Only near the ends of the solenoid does the field begin to weaken and the lines start to diverge.