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Electrical Principles and Units Flashcards

7 cards from real GROL 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 Principles and Units flashcards as text

  1. A power amplifier has a 1-watt input and a 100-watt output. What is the power gain in dB?

    Answer: 20 dB

    Gain(dB) = 10 × log(Pout/Pin) = 10 × log(100) = 10 × 2 = 20 dB.

  2. A voltage gain of 10 times corresponds to how many dB?

    Answer: 20 dB

    Gain(dB) = 20 × log(Vout/Vin) = 20 × log(10) = 20 × 1 = 20 dB.

  3. A transformer has 1000 primary turns and 100 secondary turns. If the primary voltage is 120 V, what is the secondary voltage?

    Answer: 12 V

    Vs = Vp × (Ns/Np) = 120 × (100/1000) = 12 V.

  4. A step-down transformer has 1000 primary turns and 100 secondary turns. If the secondary delivers 10 A to a load, what is the primary current (assume 100% efficiency)?

    Answer: 1 A

    Ip = Is × (Ns/Np) = 10 × (100/1000) = 1 A; current transforms inversely to voltage.

  5. What is the time constant of a series RC circuit with R = 10 kΩ and C = 0.1 μF?

    Answer: 1 ms

    τ = RC = 10,000 × 0.0000001 = 0.001 s = 1 ms.

  6. After one time constant, a capacitor in an RC charging circuit has charged to approximately what percentage of the supply voltage?

    Answer: 63%

    After one time constant, the capacitor charges to 1 − e⁻¹ ≈ 63.2% of the supply voltage.

  7. Skin effect in RF conductors causes current to:

    Answer: Flow primarily on the outer surface of the conductor

    At high frequencies, skin effect forces current to flow in a thin layer on the conductor's outer surface, increasing effective resistance.