Two identical coils, each with inductance L, share a core. If an overall inductance αL is obtained by interconnecting them, the minimum possible α is ________.
Connect the two coils in series opposition. Their net inductance is L+L−2M=2L(1−k), where M=kL and 0≤k≤1.
The smallest possible value occurs at perfect coupling k=1, when the opposing fluxes cancel and the ideal net inductance is zero. Thus the minimum possible **α=0**. Imperfect coupling leaves a positive leakage inductance.
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