Voltage, Current and Resistance — Engineering Board Exam Practice Questions

20 free engineering board exam reviewer questions on Voltage, Current and Resistance (DC Circuits), each with the correct answer and a worked solution.

  1. A copper wire 50 m long has a resistance of 0.43, ( =1.72×10-8, · m). Find its diameter.
  2. A copper wire has a resistance of R at 20° C. At what temperature will its resistance be doubled? (Use =0.00393/° C at 20° C.)
  3. A wire of resistance 4, is drawn out uniformly to twice its original length (its volume stays the same). What is its new resistance?
  4. A 12 V battery is rated 60 Ah. For how many hours can it supply a steady 5 A?
  5. A resistor has color bands yellow, violet, brown, gold. What is its resistance?
  6. A copper coil has a resistance of 100, at 20° C. Find its resistance at 70° C (temperature coefficient of copper =0.00393/° C at 20° C).
  7. A copper wire has a resistance of 12, . A second wire of the same length and material has twice the diameter. What is its resistance?
  8. Find the resistance of a copper wire 100 m long with a cross-sectional area of 2 mm2 (resistivity of copper =1.72×10-8, · m).
  9. Approximately how many electrons pass a point each second when the current is 2 A?
  10. A 5 A current flows through a wire of resistance 0.2, . What is the voltage drop along the wire?
  11. A 10 k potentiometer has its wiper set 30% of the way from one end. What is the resistance between the wiper and that end?
  12. A 1 k resistor has a 5% tolerance. Between what two values can its actual resistance lie?
  13. A resistor has color bands red, red, orange, silver. What is its value and tolerance?
  14. A resistor has color bands brown, black, red, gold. What is its value and tolerance?
  15. What is the conductance of a 50, resistor?
  16. How much work is needed to move 5 C of charge through a potential difference of 12 V?
  17. If 24 J of work moves 4 C of charge between two points, what is the voltage between them?
  18. How much charge flows in 2 minutes if the current is 0.5 A?
  19. How much current flows if 2.4 C of charge passes a point in 0.8 s?
  20. A charge of 45 C flows past a point in 15 s. Find the current.