In this article, you will find the circuit protection devices’ objective questions and answers for instrumentation, electrical, and electronics engineers.
Circuit Protection Devices Questions
The below list provides all the multiple-choice questions (MCQ) related to the circuit protection devices.
Answers are available at the bottom of the article.
1. Selective tripping is used to accomplish which of the following purposes?
| A) | To enable the application of power to emergency circuits during an overload |
| B) | To simplify the task of resetting the circuit breaker |
| C) | To reduce wear and tear on circuit breakers |
| D) | To isolate a faulty circuit without affecting other circuits |
2. A fuse current rating has which of the following definitions?
| A) | The maximum current that can flow through a circuit without causing the circuit to overheat |
| B) | The maximum current that will not”jump” an open fuse |
| C) | The maximum current that will flow through a fuse without opening the fuse |
| D) | The maximum current that will flow through a circuit if there is a direct short |
3. When a point in a circuit, where full system voltage is present, comes in direct contact with the ground or return side of the circuit, which of the following terms applies?
| A) | Excessive current |
| B) | Abnormal heating |
| C) | High resistance |
| D) | Direct short |
4. What is the current rating for a fuse with the designation F03B0R50B?
| A) | 3 amp |
| B) | 50 amp |
| C) | 1.5 amp |
| D) | 1/2 amp |
5. Which of the following is NOT a safety precaution to be observed when a fuse is changed?
| A) | Remove any corrosion from the fuse-holder before replacing a fuse |
| B) | Be sure to “tag out” the fuse-holder when you remove the fuse |
| C) | Be sure the fuse fits properly in the fuse-holder |
| D) | Remove the power from a circuit before removing and replacing a fuse |
6. Which of the following methods will provide an ABSOLUTE determination as to whether or not a fuse is open?
| A) | A voltmeter check of the fuse |
| B) | A thermometer check of the temperature of the fuse |
| C) | A visual inspection |
| D) | A check of the fuse indicator |
7. Which of the following factors is NOT used to rate fuses?
| A) | Size |
| B) | Voltage |
| C) | Current |
| D) | Time delay |
8. What is the voltage rating for a fuse with the designation F02B250V10AS?
| A) | 10 V or less |
| B) | 250 V or less |
| C) | 52 V or less |
| D) | 32 V or less |
9. Before replacing a fuse, you should check for which of the following conditions?
| A) | Proper input voltage |
| B) | Proper fit |
| C) | Both Proper fit and Proper fuse |
| D) | Proper fuse |
10. What is the new military designation for a fuse with the old, military designation F03D1R50B?
| A) | F03A125V1.5A |
| B) | F03A250V11/2A |
| C) | F03B125V1.5A |
| D) | F02B125V1.5A |
11. Selective tripping is used to cause which of the following circuit breakers to trip when there is an overload?
| A) | The least expensive |
| B) | The smallest current rating |
| C) | The closest to the fault |
| D) | The most accessible |
12. How are circuit protection devices connected to the circuit they are protecting?
| A) | In series-parallel |
| B) | In parallel |
| C) | In series |
| D) | Alongside |
13. What is the current rating for a fuse with the designation F03A125V5A?
| A) | 125 amp |
| B) | 3 amp |
| C) | 5 amp |
| D) | 1/8 amp |
14. What is the time-delay rating for a fuse with the designation F04C125V2AS?
| A) | Fast |
| B) | Delay |
| C) | Intermediate |
| D) | Standard |
15. What is the voltage rating for a fuse with the designation F03D1R00B?
| A) | 250 V or less |
| B) | 32 V or less |
| C) | 125 V or less |
| D) | 500 V or less |
16. What is the voltage rating for a fuse with the designation AGC5125V?
| A) | 25 V or less |
| B) | 12 V or less |
| C) | 125 V or less |
| D) | 51 V or less |
17. Which of the following two are circuit protection devices?
| A) | Electrical plugs and CO2 ​​cartridges |
| B) | CO2 ​​cartridges and circuit breakers |
| C) | Fuses and circuit breakers |
| D) | Fuses and electrical plugs |
18. Circuit protection devices are used for which of the following purposes?
| A) | To protect circuits |
| B) | To guard against hazardous conditions |
| C) | All of these answers |
| D) | To protect people |
19. A fuse is removed from a circuit, checked with an ohmmeter, and found to be shorted. What action should be taken?
| A) | Check the fuse with a voltmeter |
| B) | Return the fuse to the supply department |
| C) | Discard the fuse |
| D) | Put the fuse back in the circuit |
20. What is the current rating for a fuse with the designation 3AG1032V?
| A) | 1 amp |
| B) | 10 amp |
| C) | 2 amp |
| D) | 3 amp |
21. What is the total number of main components in a circuit breaker?
| A) | Five |
| B) | Three |
| C) | Two |
| D) | Four |
22. What is the current rating for a fuse with the designation F03A125V5A?
| A) | 125 amp |
| B) | 1/8 amp |
| C) | 5 amp |
| D) | 3 amp |
23. What is the time-delay rating for a fuse with the designation F03A20R0C?
| A) | Standard |
| B) | Fast |
| C) | Intermediate |
| D) | Delay |
24. What is the time-delay rating for a fuse with the designation F03A20R0C?
| A) | Delay |
| B) | Fast |
| C) | Intermediate |
| D) | Standard |
25. If the bearings of a generator were to fail, which of the following circuit conditions would probably occur?
| A) | Excessive current |
| B) | Abnormal heating |
| C) | High resistance |
| D) | Direct short |
26. What is the current rating for a fuse with the designation AGC2125V?
| A) | 3 amp |
| B) | 2 amp |
| C) | 25 amp |
| D) | 1 amp |
27. What is the voltage rating for a fuse with the designation F02B250V10AS?
| A) | 10 V or less |
| B) | 250 V or less |
| C) | 32 V or less |
| D) | 52 V or less |
28. When you perform preventive maintenance on fuses, which of the following is NOT a condition you should check?
| A) | Improper fit |
| B) | Shorted fuse |
| C) | Corrosion |
| D) | Improper fuse |
29. What is the current rating for a fuse with the designation 3AG1032V?
| A) | 1 amp |
| B) | 10 amp |
| C) | 3 amp |
| D) | 2 amp |
30. When circuit current increases beyond the designed current carrying capability of the circuit, which of the following terms applies?
| A) | High resistance |
| B) | Direct short |
| C) | Abnormal heating |
| D) | Excessive current |
31. What is the voltage rating for a fuse with the designation 3AG20125V?
| A) | 90 V or less |
| B) | 250 V or less |
| C) | 125 V or less |
| D) | 20 V or less |
32. The following actions must be taken prior to working on a circuit breaker.​
Arrange these items in the proper sequence, then select the choice below that lists the events in the proper sequence.​
A. Tag the power switch
B. Obtain the approval of the electrical officer
C. Remove power to the circuit breaker
D. Check the applicable technical manual
| A) | D, B, C, A |
| B) | B, A, D, C |
| C) | C, B, D, A |
| D) | A, B, C, D |
33. Which of the following methods should be used to check a .002 ampere fuse?
| A) | Use a megger and place a capacitor in parallel with the fuse |
| B) | Use a megger and place a capacitor in series with the fuse |
| C) | Use an ohmmeter and place a resistor in parallel with the fuse |
| D) | Use an ohmmeter and place a resistor in series with the fuse |
34. A fuse voltage rating has which of the following definitions?
| A) | The maximum voltage that can exist in a circuit if there is a direct short |
| B) | The maximum voltage across a fuse that will not jump the open fuse |
| C) | The maximum voltage across a fuse that will not cause the fuse to open |
| D) | The maximum voltage that can exist in a circuit without causing the circuit to overheat |
35. Which of the following is NOT a time-delay rating for a circuit breaker?
| A) | Long |
| B) | Short |
| C) | Instantaneous |
| D) | Standard |
36. Which of the following items is NOT checked during maintenance on a circuit breaker?
| A) | Operating mechanism smoothness |
| B) | Input power voltage |
| C) | Terminal tightness and corrosion |
| D) | Contact surfaces for pitting |
37. What should you use to remove a fuse from a clip-type fuseholder?
| A) | A pair of pliers |
| B) | A scribe |
| C) | A fusepuller |
| D) | A screwdriver |
38. What is the time-delay rating for a fuse with the designation F04C125V2AS?
| A) | Delay |
| B) | Intermediate |
| C) | Standard |
| D) | Fast |
39. Which of the following is NOT a type of trip element for a circuit breaker?
| A) | Thermal |
| B) | Mechanical |
| C) | Thermal-magnetic |
| D) | Magnetic |
40. Which of the following is a safety precaution to be observed when a fuse is checked?
| A) | When you check a fuse with an ohmmeter, be careful to avoid short circuits |
| B) | All of these answers |
| C) | When you use a voltmeter to check a low current fuse, be careful to avoid opening the fuse by excessive current from the voltmeter |
| D) | Turn the power off and discharge the circuit before the fuse is removed |
41. A circuit breaker that will trip even if the operating mechanism is held ON is known as what type of circuit breaker?
| A) | Non-trip free |
| B) | Emergency |
| C) | Trip free |
| D) | Standard |
42. What type of circuit breaker can be overridden if the operating mechanism is held ON?
| A) | Emergency |
| B) | Non-trip free |
| C) | Standard |
| D) | Trip free |
43. What is the voltage rating for a fuse with the designation 3AG20125V?
| A) | 125 V or less |
| B) | 20 V or less |
| C) | 90 V or less |
| D) | 250 V or less |
44. Which of the following conditions does NOT require the use of a circuit protection device?
| A) | High resistance |
| B) | Excessive current |
| C) | Direct short |
| D) | Abnormal heating |
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