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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. A 10 µF capacitor is connected to a 120V, 60 Hz supply. What is the capacitive reactance?

    Answer: 265 Ω

    Xc = 1/(2πfC) = 1/(2π × 60 × 10×10⁻⁶) ≈ 265 Ω.

  2. What is the power factor of a purely resistive circuit?

    Answer: 1.0

    A purely resistive circuit has voltage and current in phase, giving a power factor of 1.0 (unity).

  3. Kirchhoff's Current Law (KCL) states that:

    Answer: The sum of currents entering a node equals the sum leaving it

    KCL states that the algebraic sum of all currents at any node in a circuit equals zero (current in = current out).

  4. Two 100 Ω resistors are connected in parallel. What is the equivalent resistance?

    Answer: 50 Ω

    For two equal resistors in parallel, Req = R/2 = 100/2 = 50 Ω.

  5. Which formula correctly expresses electrical power in terms of voltage and resistance?

    Answer: P = V² / R

    Substituting I = V/R into P = VI gives P = V²/R.

  6. What is the term for the opposition that a capacitor offers to AC current flow?

    Answer: Capacitive reactance

    Capacitive reactance (Xc) is the opposition a capacitor presents to AC current, measured in ohms.

  7. In a 3-phase wye (Y) connected system, the line voltage is related to the phase voltage by:

    Answer: VL = Vφ × √3

    In a wye system, line voltage equals phase voltage multiplied by √3 (approximately 1.732).