Electrical Theory & Fundamentals Flashcards
7 cards from real Licensed Electrical Contractor practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Theory & Fundamentals flashcards as text
What is the purpose of a transformer in an electrical distribution system?
Answer: Step voltage up or down while transferring power
A transformer uses electromagnetic induction to step voltage up or down, allowing efficient long-distance power transmission and distribution at appropriate voltages.
What is 'skin effect' in AC conductors?
Answer: Tendency of AC current to flow near the outer surface of a conductor
Skin effect causes high-frequency AC current to concentrate near the conductor's outer surface, effectively reducing the usable cross-sectional area and increasing resistance.
What is the formula for capacitive reactance (XC)?
Answer: XC = 1 / (2πfC)
Capacitive reactance XC = 1/(2πfC), showing that it decreases as frequency or capacitance increases.
Three 6-ohm resistors are connected in series. What is the total resistance?
Answer: 18 ohms
Series resistors add directly: R_total = 6 + 6 + 6 = 18 ohms.
What is the significance of the power triangle in AC circuit analysis?
Answer: It shows the relationship between apparent power, true power, and reactive power
The power triangle uses the Pythagorean theorem to relate apparent power (S), true/real power (P), and reactive power (Q): S² = P² + Q².
What is the difference between a 'grounded' conductor and a 'grounding' conductor?
Answer: Grounded = current-carrying neutral; grounding = equipment safety ground
The grounded conductor is the current-carrying neutral (white), while the grounding conductor is the equipment safety ground (green/bare) that carries current only during a fault.
What phenomenon occurs when the supply frequency matches a circuit's natural resonant frequency?
Answer: Impedance is minimized and current is maximized (series resonance)
At series resonance, XL and XC cancel, leaving minimum impedance (equal to R only), which results in maximum current flow in the circuit.