When current $I$ in an inductor changes, the magnetic flux through the inductor also changes ( $Φ = L I$ ). This induces a 'back EMF' according to Faraday/Lenz: $E = - \frac{d Φ}{d t} = - \frac{d ( L I )}{d t} = - L \frac{d I}{d t}$ The negative sign indicates that the EMF opposes the change in current (it pushes back against increasing $I$ and tries to maintain decreasing $I$ ).

This medium difficulty physics question is from the chapter electromagnetic induction and ac, covering the topic of self inductance. It appeared in the 2025 exam.

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Self Inductance

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