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# Mutual Inductance

This is defined1 as "the common property of two associated electric circuits which determines, for a given rate of change of current in one of the circuits, the electromotive force induced in the other. Thus,

where e1 and i1 are in circuit 1, e2 and i2 are in circuit 2, and M is the coefficient of mutual inductance." In these equations e is the instantaneous voltage in volts, M is the mutual inductance in henrys, and di/dt is the instantaneous rate of change of current in amperes per second. It is possible to write a form similar to that of equation 3.

For steady-state sinusoidal conditions and effective values, it can be shown that

For convenience in applying to a transformer this equation has been written in terms of the effective value of the magnitude of the secondary voltage Es induced by the effective value of the primary current Ip. The units are volts, amperes, and cycles per second. If phase relations are of importance a -j should be placed in front of the final expressions of equation 8.

Last Update: 2011-05-30