When current is passed through a solenoid, the magnetic fields act almost like that of a bar magnet. One end acts as the magnetic north pole, and the other end acts as the magnetic South Pole. The magnetic curves inside the solenoid are in parallel straight lines, which indicate that the magnetic field is same at all points inside the solenoid. However, the field lines outside the solenoid travels from one pole to the other. Figure below shows the magnetic field lines inside the solenoid.
