series-aiding-a connection of coil in which the coil current produces the same direction of magnetic field for both coil.
series-opposing-a connection of coils in which the coil current produces opposing magnetic fields for each coil.
stray capacitance-a very small capacitance that exists between any two conductors separated by an insulator.for example,the capacitance can be between two wires in a wiring harness or between a single wire and a metal chassis.
stray inductance-the small inductance of any length of conductor or component lead.the effects of both stray inductance and stray capacitance are most noticeable at very high frequencies.
transformer-a device that uses the concept of mutual inductance to step up or step down an alternating voltage.
turns ratio-the ratio of the number of turns in the primary to the number of turns in the secondary of a transformer.