What measures the number of flux lines threading through a given area?

Magnetic flux is defined as the measure of the amount of magnetic field (or magnetic lines of force) passing through a specific area. It quantifies the total magnetic field that penetrates a surface, and it is mathematically represented as the product of the magnetic field strength and the area through which it passes, adjusted for the angle between the field lines and the perpendicular to the surface.

This concept is crucial in understanding various electromagnetic principles, such as Faraday's law of electromagnetic induction, where changes in magnetic flux through a coil induce an electromotive force (emf). In practical terms, measuring magnetic flux helps in analyzing the behavior of magnetic fields in different contexts, including electrical generators and transformers.

Other concepts such as magnetic intensity and magnetic field strength relate to the characteristics of the magnetic field itself, rather than the quantity of field lines through a given area. Magnetic force specifically refers to the force experienced by charged particles in a magnetic field and does not measure the density of magnetic lines. Hence, magnetic flux is the most appropriate term for measuring the number of flux lines threading through an area.