where I1 and I2 are now phasors. Note also that the emf and current in each coil are 90 out of phase.
Although the relations in Eqs. (10.48) and (10.49) may look very different than those for the ideal transformer, they are,
in fact, very similar. In particular, because all flux is contained within the core and there are no losses, the ratio between the
voltage (emf) in the primary and secondary remains the same as for the ideal transformer in Eq. (10.40). Therefore, any
transformer in which all flux is contained within the core and which has no losses behaves as an ideal transformer regardless
of the permeability of the core. This can be seen most easily from Eq. (10.44).