ABSTRACT
There are two ways of series connecting inductively coupled coils, either series aiding (so that the mutual inductance adds to the combined self-inductance of the two coils) or in series opposition (in which case the mutual inductance subtracts from the combined self-inductance of the two coils). Transformers provide us with a means of coupling a.c. power from one circuit to another without a direct connection between the two. Typical applications for transformers include stepping-up or stepping-down voltages in power supplies, coupling signals in audio and low-frequency amplifiers to achieve impedance matching and to isolate the d.c. potentials that may be present in certain types of circuit. Not all of the magnetic flux produced by the primary winding of a transformer is coupled into its secondary winding. The leakage flux increases with the primary and secondary current and its effect is the same as that produced by an inductive reactance connected in series with the primary and secondary windings.
