Which expression correctly represents the impedance of an inductor in phasor form?

Which expression correctly represents the impedance of an inductor in phasor form?

• A. Z_L = j ω L
• B. Z_L = -j ω L
• C. Z_L = R
• D. Z_L = 1/(j ω C)

Answer: (A)

In phasor analysis, an inductor follows v = L di/dt. Turning this into phasor form, differentiation becomes multiplication by jω, so V = jωLI. The impedance is Z = V/I, giving Z_L = jωL. This is a purely imaginary, frequency-dependent impedance that grows with ω, reflecting the inductive behavior where the current lags the voltage by 90 degrees. The other expressions represent different elements: a resistor has Z = R (real, in-phase voltage and current), and a capacitor has Z = 1/(jωC) = -j/(ωC) (negative imaginary, current leads voltage).

In phasor analysis, an inductor follows v = L di/dt. Turning this into phasor form, differentiation becomes multiplication by jω, so V = jωLI. The impedance is Z = V/I, giving Z_L = jωL. This is a purely imaginary, frequency-dependent impedance that grows with ω, reflecting the inductive behavior where the current lags the voltage by 90 degrees. The other expressions represent different elements: a resistor has Z = R (real, in-phase voltage and current), and a capacitor has Z = 1/(jωC) = -j/(ωC) (negative imaginary, current leads voltage).