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Physics LibreTexts

13.4: Resistance and Inductance in Series

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The impedance is just the sum of the resistance of the resistor and the impedance of the inductor:

Z=R+jlω.

Thus the impedance is a complex number, whose real part Ris the resistance and whose imaginary part Lω is the reactance. For a pure resistance, the impedance is real, and V and I are in phase. For a pure inductance, the impedance is imaginary (reactive), and there is a 90o phase difference between V and I.

The voltage and current are related by

V=IZ=(R+jLω)I.

Those who are familiar with complex numbers will see that this means that V leads on I, not by 90o, but by the argument of the complex impedance, namely tan1(Lω/R). Further the ratio of the peak (or RMS) voltage to the peak (or RMS) current is equal to the modulus of the impedance, namely R2+L2ω2.


This page titled 13.4: Resistance and Inductance in Series is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Jeremy Tatum via source content that was edited to the style and standards of the LibreTexts platform.

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