Answer: Zload = Zsource* (complex conjugate).
- A Zload = Zsource* (complex conjugate)
- B Zload = Zsource, matching magnitude and phase without conjugating it
- C Zload = 0, shorting the load terminals together largely
- D Zload = ∞, leaving the load terminals open with little current flow
Correct answer: A. Zload = Zsource* (complex conjugate)
Explanation: Maximum power transfer theorem for AC: load impedance = complex conjugate of source impedance. If source has Rs + jX_s, load should have Rs - jX_s. This is impedance matching.
In a pure inductor the current lags the voltage by 90° (energy is briefly stored in the magnetic field before current responds); in a pure capacitor the current leads the voltage by 90° (current must flow to build up charge before voltage rises) - the mnemonic "ELI the ICE man" keeps these straight.
Concept context
AC circuits, impedance, LCR series circuit, resonance, transformers, and power factor.