The current in an inductor grows as I=I₀(1- $e^(-t/τ)).$ At what time does the magnitude of self-induced EMF become one-fourth of its initial value?
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The current in an inductor grows as I=I₀(1−e^(−t/τ)). At what time does the magnitude of self-induced EMF become one-fourth of its initial value?

G1 Physics · Accepted Answer

|εL| is proportional to dI/dt=(I₀/τ)e^(−t/τ). Setting e^(−t/τ)=1/4 gives t=τln4.