what is faradys law

faradays law:

An Emf is induced when there is a change in magnetic environment of the coil, no matter how the change is produced.
i.e. when flux through the coil changes, an emf is induced  in the coil.
$$\begin{gathered} e = \frac{-d\varphi }{dt} \\ where e is the induced emf \\ \varphi is the flux \\ negative sign states that emf will induce in the direction to oppose any change occuring in it. \end{gathered}$$
$$\begin{gathered} we know flux is given by: \\ \varphi = B.A \\ \varphi = BA \cos \theta \\ where B is the magnetic field strength pas\sin g through the coil \\ A is the area of the coil \\ \theta is the angle between magnetic field and normal vector of the coil. \\ When there is some change in B or A or \theta , an emf is induced in the coil. \end{gathered}$$