[QUOTE="morgan8002;64122995"]The magnitude of the induced emf is equal to the magnitude of the rate of change of magnetic flux in the second coil. By Ohm's law this is proportional to the induced current. So the magnitude of the induced current is proportional to the magnitude of the rate of change of the magnetic flux across the second coil.
On the other hand, the magnetic flux across the second coil is proportional to the magnetic flux density, which is proportional to the current through the first coil.
So the magnitude of the induced current in the second coil is proportional to the magnitude of the rate of change of the current though the first coil.
The current in the first coil only increases slowly, so the greatest magnitude of the rate of change of the current in the first coil is when the switch is opened and the current suddenly drops to 0.[/QUOTE
Thank you so much ! It's so much more clear now