Magnetic flux is a measure of the magnetic field passing through a given surface. It is defined as the product of the magnetic field strength and the surface area perpendicular to the magnetic field. Mathematically, magnetic flux can be expressed as Φ = B.A, where Φ is the magnetic flux, B is the magnetic field strength, and A is the surface area.

Faraday's law of electromagnetic induction states that a changing magnetic flux through a circuit induces an electromotive force (EMF) in the circuit. This EMF is proportional to the rate of change of the magnetic flux through the circuit. This relationship is expressed mathematically as EMF = -dΦ/dt, where EMF is the induced electromotive force, Φ is the magnetic flux, and t is time.