Final answer:
A changing magnetic flux induces an electric field because of the principles of electromagnetic induction governed by Faraday's law. The magnetic flux is defined as the product of the magnetic field strength, the area it passes through, and the cos of the angle relative to the area's perpendicular. Any variances in these properties can induce an emf that, according to Lenz’s law, opposes the original flux change.
Step-by-step explanation:
Why does a changing magnetic flux induce an electric field? This phenomenon is the cornerstone of electromagnetic induction, a concept that is central to understanding how many electrical devices work. According to Faraday's law of induction, a changing magnetic flux through a surface, like the loop of a wire, will induce an electromotive force (emf) and thus an electric field in the conductor.
The key quantity in this process is the magnetic flux (Ø), defined as Ø = BA cos θ, where B is the magnetic field strength, A is the area through which the field lines pass, and θ is the angle between the field lines and the perpendicular to the area. Essentially, the magnetic flux is the amount of magnetic field passing through a given area. When there is a change in magnetic flux due to the movement of a magnet towards a coil or vice versa, the variation in the field can be caused by changes in the field strength (B), the area (A), or the orientation (θ) of the field with respect to the area. This change in flux creates the induced emf, and due to Lenz's law, the induced field will oppose the change in flux.