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  • Question

  • A 120 V lamp-dimming circuit is controlled by a rheostat and protected from excessive current by a 3 A fuse. To what minimum resistance value can the rheostat be set without blowing the fuse? Assume a lamp resistance of 20 ohms.


  • Options
  • A. 40 Ω
  • B. 4 Ω
  • C. 2 Ω
  • D. 20 Ω

  • Correct Answer
  • 20 Ω 

    • More questions

    • 1. The induced voltage across a coil with 250 turns that is located in a magnetic field that is changing at a rate of 8 Wb/s is

    • Options
    • A. 1,000 V
    • B. 2,000 V
    • C. 31.25 V
    • D. 3,125 V
      • Discuss
    • 2. A 10 Ω resistor, a 90 mH coil, and a 0.015 µF capacitor are in series across an ac source. The impedance magnitude at 1,200 Hz below fr is

    • Options
    • A. 1,616 Ω
    • B. 161 Ω
    • C. 3,387 Ω
    • D. 1,771 Ω
      • Discuss
    • 3. Approximately how much current flows through a 3.3 MΩ resistor across a 30 V source?

    • Options
    • A. 9 µA
    • B. 90 µA
    • C. 900 µA
    • D. 9000 µA
      • Discuss
    • 4. In a certain transformer, the input power to the primary is 120 W. If 8.5 W are lost to the winding resistance, what is the output power to the load, neglecting any other issues?

    • Options
    • A. 0 W
    • B. 14.1 W
    • C. 111.5 W
    • D. 1,020 W
      • Discuss
    • 5. A balanced load is one in which all the impedances are equal.

    • Options
    • A. True
    • B. False
      • Discuss
    • 6. A 470 Ω resistor, a 220 Ω resistor, and a 100 Ω resistor are all in parallel. The total resistance is approximately

    • Options
    • A. 790 Ω
    • B. 470 Ω
    • C. 60 Ω
    • D. 30 Ω
      • Discuss
    • 7. What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV?

    • Options
    • A. 4 kVA
    • B. 0.25 kVA
    • C. 16 kVA
    • D. 8 kVA
      • Discuss
    • 8. In a series RLC circuit, the current is minimum at resonance.

    • Options
    • A. True
    • B. False
      • Discuss
    • 9. In a series circuit, the individual powers are additive.

    • Options
    • A. True
    • B. False
      • Discuss
    • 10. If the voltage is stepped up, the current is stepped down, and vice versa.

    • Options
    • A. True
    • B. False
      • Discuss

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