Question 1
A 15 A breaker feeding a small room trips when a space heater and toaster are used on the same circuit. What is the most likely cause?
Question 2
A homeowner reports that a 15 A breaker trips whenever a vacuum and a portable heater are used on the same receptacle. Which is the MOST likely cause?
Question 3
A 7.5 kW three-phase motor starts normally but trips the overload relay after several minutes of operation under load. Voltage remains within tolerance and phase currents are balanced and slightly above nameplate full-load current. What is the MOST probable cause?
Question 4
A 15 A lighting circuit in a dwelling frequently trips its breaker immediately after being turned on. Megger testing between the ungrounded conductor and the equipment bonding conductor shows very low resistance. What is the MOST appropriate corrective action?
Question 5
When troubleshooting a tripped breaker, what should be done before resetting it?
Question 6
What is the primary diagnostic step when troubleshooting an intermittent 'nuisance trip' of an AFCI circuit breaker?
Question 7
What is the primary diagnostic step when troubleshooting an intermittent 'nuisance trip' of an AFCI breaker in a bedroom circuit?
Question 8
A lighting circuit shows nuisance tripping of the breaker shortly after being turned on. Which of the following is the MOST likely cause?
Question 9
On a residential job, a homeowner has multiple space heaters plugged into one receptacle strip and reports frequent breaker trips. What is the most likely cause?
Question 10
A device used to open or close a circuit manually under normal load conditions is called a:
Question 11
In a Canadian residential installation, which type of device is commonly used to protect receptacles in bathrooms from shock hazards?
Question 12
Which device is designed to protect people from electric shock due to ground faults in receptacle circuits?
Question 13
A homeowner reports that a breaker trips whenever a toaster and a kettle are used on the same kitchen circuit. What is the most likely cause?
Question 14
A circuit breaker trips after several minutes whenever multiple appliances are used on the same circuit. What is the most likely cause?
Question 15
A lighting circuit repeatedly trips its breaker when several luminaires are turned on together. The breaker and conductor appear correctly sized. Which issue is most likely?
Question 16
A homeowner reports that a 15 A breaker trips whenever a space heater and a microwave are used at the same time on the same receptacle circuit. What is the most likely cause?
Question 17
Which statement best describes the difference between an overload and a short circuit in a motor branch circuit?
Question 18
Which statement best describes the function of a GFCI device?
Question 19
A homeowner reports that a 15 A breaker trips when a space heater and hair dryer are both used on the same receptacle circuit. Measurements show the heater draws 12 A and the hair dryer draws 10 A at 120 V. What is the BEST explanation?
Question 20
What does a GFCI device primarily protect against?
Question 21
On a lighting circuit, several fixtures go out, but the breaker has not tripped and some lights on the same circuit still work. Which is the most likely cause?
Question 22
An outdoor receptacle on a porch is GFCI protected and frequently trips during rainy weather even with no load plugged in. Which is the most likely cause?
Question 23
A 10 hp motor has a full-load current rating of 28 A. For short-circuit and ground-fault protection, what is a reasonable breaker size if the code allows up to 250 percent of motor full-load current for the inverse time breaker in this case?
Question 24
A homeowner reports that a 15 A bedroom circuit breaker trips whenever they use a portable space heater and a vacuum at the same time. What is the most likely cause?
Question 25
A bathroom GFCI receptacle trips immediately when a hair dryer is plugged in and turned on, but the dryer works on other GFCI-protected circuits. What is the most likely issue?
Question 26
A homeowner complains that a 15 A kitchen counter circuit trips when a toaster and a coffee maker are used at the same time. What is the MOST likely issue?
Question 27
When troubleshooting a lighting circuit that repeatedly trips a breaker immediately when turned on, which issue is MOST likely?
Question 28
A 2 hp, 240 V single-phase motor has been repeatedly tripping its thermal overload relay, but the branch-circuit breaker does not trip. Which conclusion is most likely?
Question 29
A 240 V, single-phase motor starts normally but trips the breaker after several minutes of running at rated load. What is the most likely cause?
Question 30
A bathroom 120 V, 20 A branch circuit supplies a 12 A hair dryer and a 10 A portable heater at the same time. What is the MOST likely reason the breaker trips?