<Li> Balun - a transformer which matches a balanced transmission line to an unbalanced one . </Li> <Li> Bifilar coil - a coil wound with two parallel, closely spaced strands . If AC currents are passed through it in the same direction, the magnetic fluxes will add, but if equal currents in opposite directions pass through the windings the opposite fluxes will cancel, resulting in zero flux in the core . So no voltage will be induced in a third winding on the core . These are used in instruments and in devices like Ground Fault Interrupters . They are also used in low inductance wirewound resistors for use at RF frequencies . </Li> <Li> Audio transformer - A transformer used with audio signals . They are used for impedance matching . <Ul> <Li> Hybrid coil - a specialized audio transformer with 3 windings used in telephony circuits to convert between two - wire and four - wire circuits </Li> </Ul> </Li> <Ul> <Li> Hybrid coil - a specialized audio transformer with 3 windings used in telephony circuits to convert between two - wire and four - wire circuits </Li> </Ul>

What is the purpose of no volt coil in a dc motor