Transformers -- Why output current decreases for step-up xfmr? So I've been wondering if anyone in PF could explain to me the reasons currents can either increase or decrease in a transformer depending on the wiring. I understand electromagnetic fields/forces, magnetic flux, and I even could tell you the input and output currents given a transformer with the number of turns of each winding. However, I never learned the reason why in, for example, a step up transformer is able to increase voltage but the current decrease. I understand that these values have to inversely change from one another to keep constant power, but I want to know why a changing magnetic flux through more coils creates less current and greater voltage and why changing the flux through fewer coils creating lower voltage and higher current. Any help?