Now, I know the law of inductors, so when the switch turns on (it allows current to pass), there is a fixed voltage across the inductor. The current ramps up linearly and the slope is dependent on the value of the voltage source and the inductance.
Now, when the switch turns off and the current is decreasing in a very short amount of time, according to the law of the inductor, the voltages is inverted and therefore the voltage also changes polarity on the secondary side and current can flow on the secondary.
To my question: What determines the speed that the current is decreasing on the primary? I would suspect that it depends on the value of the impedance of the secondary side. The idea would be that a low impedance can accept (or let's say demand) a bigger amount of current and therefore allow a faster teardown of the field. I would suspect, that on the secondary side, current is the "driving" force and the exact voltage value is a result of impedance and current? So is it correct that the secondary impedance determines how fast the energy of the magnetic field is transferred to the secondary or is it "just" dependent on the output voltage instead?