This bridge (Fig.1) measures mutual inductance in terms of a known self-inductance. The same bridge, slightly modified, was used by Campbell to measure a self-inductance in terms of known mutual inductance.

Fig. 1. Heaviside mutual inductance bridge

Let , *M*= unknown mutual Inductance ,

*L*_{1}= self-inductance of secondary of mutual inductance ,

*L*_{2}= known self-inductance ,

*R*_{1}, *R*_{2}, *R*_{3}, *R*_{4}= non inductive resistors,

At balance voltage drop between b and c must equal the voltage drop between d and c. Also the votage drop across a-b-c must equal the voltage drop across a-d-c. Thus we have the following equations at balance.

and,

..

Thus,

and,

It is clear from Eqn. (2), that *L*_{1}, the self inductance of the secondary of the mutual inductor must be known in order that *M* be measured by this method.

In case, *R*_{3}=*R*_{4}, we get,

This method can be used for measurement of self-inductance.