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Circuit Theory and Calculations Flashcards

6 cards from real 309A practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Circuit Theory and Calculations flashcards as text

  1. What is the total resistance of three resistors connected in series with values of 10 Ω, 20 Ω, and 30 Ω?

    Answer: 60 Ω

    In a series circuit, total resistance is the sum of all individual resistances: 10 + 20 + 30 = 60 Ω. Current flows through each resistor sequentially.

  2. A 240 V single-phase circuit supplies a 5 kW resistive load. What is the current draw?

    Answer: 20.83 A

    Using P = V × I, we get I = P/V = 5000/240 = 20.83 A. For a purely resistive load, the power factor is 1, so no correction is needed.

  3. What is the power factor of a circuit with a real power of 8 kW and an apparent power of 10 kVA?

    Answer: 0.80

    Power factor = Real Power / Apparent Power = 8 kW / 10 kVA = 0.80. This means 80% of the apparent power is doing useful work.

  4. In a parallel circuit with two resistors of 12 Ω and 6 Ω, what is the total resistance?

    Answer: 4 Ω

    For parallel resistors: 1/Rt = 1/R1 + 1/R2 = 1/12 + 1/6 = 1/12 + 2/12 = 3/12, so Rt = 12/3 = 4 Ω.

  5. A conductor carries 15 A and has a resistance of 0.5 Ω. What is the voltage drop across it?

    Answer: 7.5 V

    Using Ohm's Law: V = I × R = 15 A × 0.5 Ω = 7.5 V. This represents the voltage lost as heat in the conductor.

  6. What is the impedance of a series RL circuit with R = 30 Ω and XL = 40 Ω?

    Answer: 50 Ω

    Impedance Z = √(R² + XL²) = √(900 + 1600) = √2500 = 50 Ω. The impedance combines resistance and inductive reactance using the Pythagorean theorem.