USCG Exam PracticeAC circuits and theory
In an AC circuit containing both resistance and inductive reactance, the total opposition to current flow is called impedance. Which formula correctly expresses impedance?
- A. Z = R + XL
- ✓ Z = √(R² + X²)Correct
- C. Z = R × XL
- D. Z = XL − R
Why B is correct
NEETS Mod. 2 §4-1 states that resistance and reactance cannot be added arithmetically because the reactive voltage is 90° out of phase with the resistive voltage; they must be combined vectorially as Z = √(R² + X²). Simple arithmetic addition (option A) ignores the phase relationship.
Cited:NEETS Mod. 2 §4-1