These assumptions ensure that the magnetization current under no load condition is vanishingly small and can be ignored. Further, all time varying flux produced by the primary winding will follow the magnetic path inside the core and link to the secondary coil without any leakage. If N₁ and N₂ are the number of turns in the primary and the secondary windings respectively, the induced emfs are

                                (5.12a)

                                 (5.12b)

(The polarities are marked, hence negative sign is omitted. The induced emf is +ve at the dotted end of the winding.)

                                  (5.13)