Hi, I'm trying to figure out what phase differences take place with an ideal transformer. This is what I have figured out so far: If you apply an AC current to the primary coil then you will get an alternating flux in the primary and secondary coils simultaneously therefore the fluxes are in phase. The induced emf at the secondary will be 90 degrees out of phase to its flux which follows on from Faraday's Law. I'm trying to figure out the phase differences of the back emf's. Will the back emf in the primary coil also be 90 degrees out of phase and therefore be in phase with the emf of the secondary? I'm not sure about the back emf of the secondary? Is there anything that is 180 degrees out of phase? Thank you for any help given.