Transformers and Electrical Theory Flashcards
6 cards from real Journeyman Electrician’s Exam practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Transformers and Electrical Theory flashcards as text
What is the power factor of a purely resistive AC circuit?
Answer: 1.0
A purely resistive circuit has voltage and current in phase (0° phase angle), resulting in a power factor of 1.0 (unity).
Apparent power in an AC circuit is expressed in which unit?
Answer: Volt-amperes (VA)
Apparent power is the product of RMS voltage and RMS current expressed in volt-amperes (VA) or kilovolt-amperes (kVA).
A circuit has 240V applied and draws 20 amperes. Using Ohm's Law, what is the circuit resistance?
Answer: 12 ohms
R = V ÷ I = 240 ÷ 20 = 12 ohms.
What is the correct formula for calculating true (real) power in a single-phase AC circuit?
Answer: P = V × I × PF
True power (watts) = Voltage × Current × Power Factor; omitting PF gives apparent power in VA, not real power.
A series circuit has a resistance of 6 ohms and an inductive reactance of 8 ohms. What is the total impedance?
Answer: 10 ohms
Z = √(R² + XL²) = √(6² + 8²) = √(36 + 64) = √100 = 10 ohms.
What is the inductive reactance (XL) of a 0.2 Henry inductor at 60 Hz?
Answer: 75.4 ohms
XL = 2πfL = 2 × 3.14159 × 60 × 0.2 = 75.4 ohms.