= Solution
For a fixed linear circuit, <self-inductance> relates the <magnetic flux linkage> produced by its own current to that current: $\Lambda=LI$, with $\Lambda=\sum_{\rm turns}\Phi_B$. The self-induced <electromotive force> is $\mathcal E=-d\Lambda/dt=-L\,dI/dt$ when $L$ is constant. Its unit is the henry, $1\,\mathrm H=1\,\mathrm{Wb/A}$.
<mutual inductance> relates the linkage in one circuit to current in another: $\Lambda_2=M_{21}I_1$ and $\Lambda_1=M_{12}I_2$. For stationary reciprocal linear media, $M_{12}=M_{21}=M$ with consistently oriented turns, and $\mathcal E_2=-M\,dI_1/dt$. Orientation fixes the sign. The coupled magnetic <energy> is $W=\tfrac12L_1I_1^2+\tfrac12L_2I_2^2+MI_1I_2$, so positivity requires $M^2\leq L_1L_2$. Moving coils or nonlinear cores require differentiation of the full linkage rather than treating the <inductance> as a constant.
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