Energy and Power — Engineering Board Exam Practice Questions

22 free engineering board exam reviewer questions on Energy and Power (DC Circuits), each with the correct answer and a worked solution.

  1. A 1000 W heater is designed for 120 V. If it is connected to 60 V (resistance unchanged), what power does it dissipate?
  2. A resistor dissipates 2 W when connected across a battery. A second identical resistor is connected in parallel with the first. What total…
  3. A series circuit has V=24 V and R1=100, , and R1 dissipates 4 W. What is R2?
  4. A 5 kW load is supplied through a line of total resistance 0.5, . How much power is lost in the line if the supply voltage is 230 V…
  5. A 100 W and a 40 W lamp, both rated 120 V, are connected in series across 120 V. How much power does the 40 W lamp dissipate (assume fixed…
  6. The source in the circuit shown is 12 V and the resistor is 4, . How much energy does the resistor use in 2 hours?
  7. The source in the circuit shown is 24 V and the resistor is 6, . How much power does the resistor dissipate?
  8. A 40 W lamp is on for 5 hours each day. At P12 per kWh, how much does it cost for a 30-day month?
  9. Two resistors, 10, and 15, , are connected in series across 50 V. What is the total power dissipated?
  10. A device uses 750 W for 2 hours. How much energy does it use?
  11. An electric heater is rated 2000 W at 230 V. What current does it draw?
  12. A 60 W, 120 V lamp has what resistance when operating?
  13. If the voltage across a fixed resistor is doubled, the power it dissipates
  14. A motor takes 1.2 kW from the supply and delivers 1 hp (746 W) at the shaft. What is its efficiency?
  15. A 12 V battery rated 100 Ah stores how much energy?
  16. A 100, resistor is rated 12 W. What is the maximum voltage that can be applied across it?
  17. A 220, resistor is rated 14 W. What is the maximum current it can carry without exceeding its rating?
  18. A 1500 W heater runs 4 hours a day for 30 days. At P11.50 per kWh, what is the cost?
  19. The source in the circuit shown is 48 V and the resistor is 12, . How much power does the source deliver?
  20. A 100, resistor is connected across a 10 V source. What power does it dissipate?
  21. A 20, resistor carries a current of 0.5 A. How much power does it dissipate?
  22. A resistor carries 3 A when connected to 12 V. What power does it dissipate?