The graph between E and t is as shown in Fig. Here as the magnet approaches the coil, E will go on increasing up to b. When the magnet fully enters the coil given by point c, there is no change in magnetic flux, it is shown by c in Fig.
And again when it is coming out from the coil, the value of E increases in reverse direction.
Area below E-t graph gives the magnetic flux because
Et = flux [∵ \(\frac{d\phi}{dt}\) = E or dΦ = E dt]
