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Electrical Calculations and Theory Flashcards

7 cards from real IEC 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 Calculations and Theory flashcards as text

  1. A 120V circuit has a 15Ω load. How much power does the load consume?

    Answer: 960W

    P = V² / R = 120² / 15 = 14,400 / 15 = 960W.

  2. Inductive reactance (XL) increases when:

    Answer: Frequency increases

    XL = 2πfL, so inductive reactance is directly proportional to frequency.

  3. What is the apparent power (VA) of a 3-phase, 208V system drawing 25A per phase?

    Answer: 9,004 VA

    S = √3 × V × I = 1.732 × 208 × 25 ≈ 9,004 VA.

  4. Two 100W, 120V incandescent lamps are connected in series across 120V. What is the total power consumed?

    Answer: 50W

    Each lamp's resistance = 120²/100 = 144Ω; series total = 288Ω; P = 120²/288 = 50W.

  5. The power factor of a purely resistive circuit is:

    Answer: 1.0

    A purely resistive circuit has no reactive power, so PF = real power / apparent power = 1.0.

  6. A conductor's resistance increases when its:

    Answer: Temperature increases

    Most conductors have a positive temperature coefficient, meaning resistance rises as temperature increases.

  7. What is the skin effect in AC conductors?

    Answer: Current concentrates near the outer surface, increasing effective AC resistance

    At AC frequencies, current density is highest near the conductor surface, reducing usable cross-section and increasing resistance.