I have an NPN transistor that's connected over a 12V adapter. I have tried using a potentiometer to change the resistance of the incomming current. Even if i take the resistance down to 0, I end up with at most 11 Volts when measuring over the magnet.
I have measure the energy without the transistor, in that case it's 12V. Is this expected behaviour of a transistor or is something wrong?