Extra exam question E7C04
Subelement E7, PRACTICAL CIRCUITS· Group E7C
How does an impedance-matching circuit transform a complex impedance to a resistive impedance?
- A.It introduces negative resistance to cancel the resistive part of impedance
- B.It introduces transconductance to cancel the reactive part of impedance
- C.It cancels the reactive part of the impedance and changes the resistive part to the desired value (correct answer)
- D.Reactive currents are dissipated in matched resistances
WhyAn impedance-matching circuit transforms a complex impedance to a resistive one by canceling the reactive part and changing the resistive part to the desired value. An impedance-matching circuit transforms a complex impedance into a purely resistive one by canceling out the reactive (imaginary) part of the impedance while simultaneously adjusting the remaining resistive part to whatever value is actually desired, the combined tuning action that lets a matching network present a clean resistive load, answer C. It doesn't work by introducing negative resistance or transconductance to cancel reactance, and it isn't a matter of simply dissipating reactive currents in matched resistances, that would waste power rather than matching impedance.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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