self inductance

Question

Induced EMF in inductor L with changing current di/dt is:

RankGuru · Accepted Answer

When current $I$ in an inductor changes, the magnetic flux through the inductor also changes ($\Phi = LI$). This induces a 'back EMF' according to Faraday/Lenz:
$E = -\frac{d\Phi}{dt} = -\frac{d(LI)}{dt} = -L \frac{dI}{dt}$
The negative sign indicates that the EMF opposes the change in current (it pushes back against increasing $I$ and tries to maintain decreasing $I$).

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