Ohm's Law — Engineering Board Exam Practice Questions

22 free engineering board exam reviewer questions on Ohm's Law (DC Circuits), each with the correct answer and a worked solution.

  1. A lamp has a hot resistance of 240, and a cold resistance of 20, . It is switched on at 120 V. How many times larger is the initial (cold)…
  2. A resistor connected to a source draws 2 A. When a 4, resistor is added in series, the current falls to 1.5 A. Find the source voltage.
  3. In the circuit shown, the source is 24 V and the resistor is 8, . What would the ammeter read if the source voltage were doubled?
  4. A 100, resistor must carry 150 mA. What voltage must be applied?
  5. A heater element draws 5 A at 230 V. What resistance does it present?
  6. What is the current through a 33 k resistor connected across a 9 V battery?
  7. A voltmeter reads 8.4 V across a resistor and an ammeter in series reads 42 mA. What is the resistance?
  8. A 12 V battery with internal resistance 0.4, is connected to a 5.6, load. What current flows?
  9. A battery of emf 12 V and internal resistance 0.5, delivers 2 A to a load. What is the terminal voltage?
  10. A resistor draws 20 mA at 6 V and 50 mA at 15 V. Find its resistance.
  11. The voltage across a resistor is tripled and, at the same time, its resistance is halved. By what factor does the current change?
  12. A 4.7 k resistor carries 2.5 mA. What is the voltage across it?
  13. In the circuit shown, the source is 36 V and the resistor is 9, . What does the ammeter read?
  14. In the circuit shown, the source is 12 V and the resistor is 4, . What does the ammeter read?
  15. For a fixed voltage, if the resistance in a circuit is halved, the current
  16. If the voltage across a fixed resistor is tripled, the current is
  17. A resistor draws 2 A from a 120 V source. If the source voltage falls by 10%, what current will flow (resistance unchanged)?
  18. What voltage is needed to drive 60 mA through a 330, resistor?
  19. A device connected to a 24 V supply draws 500 mA. Find its resistance.
  20. A device connected to a 9 V supply draws 30 mA. Find its resistance.
  21. A 4, resistor is connected across a 12 V source. How much current flows?
  22. A 6, resistor is connected across a 24 V source. How much current flows?