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Electrical Theory and Principles 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 Theory and Principles flashcards as text

  1. The time constant (τ) of an RL circuit is defined as:

    Answer: τ = L / R

    The time constant of an RL circuit is τ = L/R, representing the time for current to reach approximately 63.2% of its final value.

  2. What is the phase angle in a circuit with R = 30 Ω and XL = 40 Ω?

    Answer: 53.1°

    θ = arctan(XL/R) = arctan(40/30) = arctan(1.333) ≈ 53.1°.

  3. Reactive power in an AC circuit is measured in:

    Answer: Volt-amperes reactive (VAR)

    Reactive power, which represents energy stored and released by inductors and capacitors, is measured in volt-amperes reactive (VAR).

  4. A 240V circuit draws 20A with a power factor of 0.8. What is the true power consumed?

    Answer: 3840 W

    True power P = V × I × PF = 240 × 20 × 0.8 = 3840 W.

  5. Which of the following materials is classified as a semiconductor?

    Answer: Silicon

    Silicon is a semiconductor, having electrical conductivity between that of conductors and insulators.

  6. The skin effect in AC conductors causes current to:

    Answer: Concentrate toward the outer surface of the conductor

    At higher AC frequencies, current tends to flow near the outer surface (skin) of the conductor, increasing effective resistance.

  7. What is the total impedance of a series circuit with R = 6 Ω, XL = 10 Ω, and XC = 2 Ω?

    Answer: 10 Ω

    Z = √(R² + (XL - XC)²) = √(36 + (10-2)²) = √(36 + 64) = √100 = 10 Ω.