Vol. EE Reference
Chapter 9 Circuit Schematic Symbols

Mutual Inductors

types of mutual inductors

Mutual inductors are inductors that capitalize the effect of mutual inductance. Mutual inductance occurs when the magnetic field of an inductor induces a magnetic field in an adjacent inductor. Mutual inductance is the basis of  making transformers. 

Above are the most common schematic symbols of types of mutual inductors.