Journeyman Electrician Practice Test
Journeyman Electrician Motors & Air Conditioning Practice Questions
Motors & Air Conditioning makes up 5 of every 50 questions on a Tigertest Journeyman Electrician practice test. Here are 10 of the 20 questions on it, each with the answer and the reason.
Updated by the Tigertest team. Based on the 2023 National Electrical Code (NFPA 70) and standard electrical theory. Original questions; 50 per test, 70% to pass. State licensing law not included.
1. The motor branch-circuit breaker or fuse sized from the 250 or 175 percent table protects against:
- A.Low supply voltage
- B.Short circuits and ground faults
- C.Running overloads
- D.Failure to start
Answer: B. The motor branch-circuit short-circuit and ground-fault device is sized high enough to carry starting current. It does not protect against running overloads; the overload device does.
2. For sizing motor branch-circuit conductors and short-circuit protection, full-load current is taken from:
- A.Measured running current
- B.The starter rating
- C.The motor nameplate
- D.The NEC full-load current tables
Answer: D. For general motor applications, conductors, short-circuit and ground-fault protection and disconnects are sized from the table full-load currents, not the nameplate. Overloads use the nameplate.
3. Separate motor overload protection is sized from the motor's:
- A.Nameplate full-load current
- B.Branch breaker rating
- C.Table full-load current
- D.Locked-rotor current
Answer: A. Overload devices are sized from the nameplate full-load current, because they protect that particular motor from overheating.
4. A motor has a marked service factor of 1.15. Before any increase for a motor that will not start, its overload may be rated at no more than what percent of nameplate current?
- A.140 percent
- B.100 percent
- C.125 percent
- D.115 percent
Answer: C. Motors with a service factor of 1.15 or more, or a marked temperature rise of 40°C or less, get overloads at 125 percent of nameplate current. All others get 115 percent. Only if that overload trips on starting may it be raised, to 140 or 130 percent.
5. The ampere rating of a motor-circuit disconnect for a motor of 1000 V or less must be at least what percent of FLC?
- A.125 percent
- B.150 percent
- C.115 percent
- D.100 percent
Answer: C. A motor disconnect must have an ampere rating of at least 115 percent of the motor's table full-load current.
6. For an ordinary squirrel-cage motor, an inverse time breaker may be rated up to what percent of full-load current?
- A.250 percent
- B.300 percent
- C.800 percent
- D.175 percent
Answer: A. The motor protection table allows 250 percent for inverse time breakers, 175 percent for dual-element time-delay fuses and 300 percent for nontime-delay fuses.
7. For an ordinary squirrel-cage motor, a dual-element time-delay fuse may be rated up to what percent of full-load current?
- A.300 percent
- B.125 percent
- C.250 percent
- D.175 percent
Answer: D. Dual-element (time-delay) fuses for most AC motors are limited to 175 percent of full-load current in the motor branch-circuit protection table.
8. A motor's table full-load current is 14 A. What is the minimum branch-circuit conductor ampacity?
- A.35 A
- B.17.5 A
- C.14 A
- D.16.1 A
Answer: B. Conductors are 125 percent of FLC: 14 x 1.25 = 17.5 A. 16.1 A uses the 115 percent overload figure by mistake.
9. A squirrel-cage motor has a table FLC of 28 A. What is the maximum inverse time breaker without using the next-size-up rule?
- A.84 A
- B.70 A
- C.35 A
- D.49 A
Answer: B. 28 x 250 percent = 70 A, which is a standard size. 49 A is the 175 percent fuse figure and 35 A is the conductor percentage.
10. A motor's table FLC is 34 A. Using 250 percent and the next-size-up allowance, what inverse time breaker is allowed?
- A.85 A
- B.100 A
- C.80 A
- D.90 A
Answer: D. 34 x 2.5 = 85 A, which is not a standard size, so the next higher standard rating of 90 A may be used.
Practice all 20 motors & air conditioning questions, and the rest of the 200-question bank, in the free Journeyman Electrician training sets. Questions you miss come back until you have mastered them.
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