A magnetic field is an invisible area around a magnet or a current-carrying conductor where magnetic forces are exerted. It is the magnetic field that enables magnets to attract or repel each other. The strength of a magnetic field is determined by the magnetic field lines, which represent the direction and intensity of the magnetic force.

To understand magnetic fields, consider a bar magnet. When imagining the magnetic field lines surrounding the magnet, envision them originating from the magnet's north pole, looping around to the south pole, and completing the circuit outside the magnet. These lines create a continuous path for the magnetic force to travel.

Magnetic fields can also be generated by electric currents flowing through conductors. According to Ampere's law, an electric current creates a magnetic field that wraps around the conductor in the form of concentric circles. The strength of the magnetic field depends on the magnitude of the current and the distance from the conductor.

The concept of magnetic fields can be further illustrated through the experiment of placing a magnet near a cardboard covered with iron filings. When the magnet is brought closer to the cardboard, the iron filings align themselves along the magnetic field lines, revealing the pattern of the magnetic field.