Dipoles and monopoles:

A pair of magnetic poles is called a dipole. A lone pole, like positive pole in a proton, is known as monopole.

Magnetic monopoles do not exist in nature ordinarily. If they could somehow be conjured up, all types of fascinating things may happen. Scientists are researching this to see if they can generate artificial magnetic monopoles.

At first you might think that the magnetic field around the current-carrying wire is created by a monopole, or that there are not any poles at all, as the concentric circles do not converge anywhere. But in fact, you can think of any half-plane, having the edge along the line of the wire, as a magnetic dipole, and the lines of flux as going around once from north face of the half-plane to the south face.

The lines of flux in the magnetic field connect the 2 poles always. Some flux lines are straight and some are curved. The largest flux density, or field strength, around the bar magnet is near poles, where lines converge. Around the current carrying wire, the most field strength is near the wire.