in coil 2. This current in coil 2 is produced by the collapsing

magnetic field of coil 1.

(1) *Factors Affecting Mutual Inductance*. The mutual

inductance of two adjacent coils is dependent upon the physical

dimensions of the two coils, the number of turns in each coil,

the distance between the two coils, the relative positions of

the axes of the two coils, and the permeability of the core.

FIGURE 23. MUTUAL INDUCTANCE.

(2) *Coefficient of Coupling*. The COEFFICIENT OF COUPLING

between the two coils is equal to the ratio of the flux cutting

one coil to the flux originated in the other coil. If the two

coils are so positioned with respect to each other that all of

the flux of one coil cuts all the turns of the other, the coils

are said to have a unity coefficient of coupling. It is never

exactly equal to unityone, but it approaches this value in

certain types of coupling devices. If all the flux produced by

one coil cuts only half the turns of the other coil, the

coefficient of coupling is 0.5. The coefficient of coupling is

designated by the letter K.