What are the invisible lines that outline the magnetic field around a magnet called?

The invisible lines that outline the magnetic field around a magnet are referred to as magnetic field lines. These lines are a conceptual tool used to visualize how the magnetic field behaves in space. They illustrate the direction and strength of the magnetic field, with the density of the lines indicating the strength of the field—where lines are closer together, the magnetic field is stronger.

Magnetic field lines emanate from the north pole of a magnet and loop around to return to the south pole, forming a continuous loop. This visual representation helps in understanding how magnetic forces interact with other magnetic materials and how fields combine in different configurations.

By describing the pattern and direction of the magnetic field, magnetic field lines enhance the understanding of electromagnetic principles and are foundational in physics when studying magnetism and its applications.