The region around a magnet where the magnetic force is exerted is known as magnetic field. Magnetic field is the area around a magnet, a magnetic object or an electric charge in which magnetic force is exerted. Magnetic fields are created by moving electric charge. Magnetic field is measured by its strength and by the direction it points. The strongest external magnetic fields are near the poles. A magnetic north pole will attract the south pole of another magnet, and repel a north pole. In a bar magnet the magnetic field lines can be traced out with the use of a compass.