 Solution

ID: past-exam-of-the-physics-2-paper-of-the-university-of-oxford/2018/9/iii/solution

V = L d I_{L} / d t

. In the steady AC solution with no added constant electric current,

Z_{L} = iω L, I_{L} (t) = \frac{V _{0}}{ω L} sin ω t = \frac{V _{0}}{ω L} cos (ω t - π /2) .

The electric current lags the voltage by $π /2$ . An ideal inductor can also sustain an arbitrary DC current, fixed by initial conditions; it is excluded from this steady sinusoidal comparison.

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