12.2 Induced electromotance in Terms of mutual Inductance a change in Ia induces the electromotance in b ab This equation is convenient to calculate vh, since M and dIa/dt are easy to measure Note that we can write aA Db=fbE·d1=fb(-+)·dl, where a is the vector potential at b produced by la Similarly, a change in Ib induces the electromotance n a