semplr.

Exams · Certifications · Licensing

Journeyman Electrician Exam (NEC-based)

Overcurrent protection: practice questions

Our Journeyman Electrician bank has 12 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.

Start the free mock exam

Question 1

Which breaker should feed a 30-amp, 240-volt dryer circuit with 10 AWG copper?

  1. 20-amp two-pole
  2. 40-amp single-pole breaker with a neutral
  3. 50-amp two-pole
  4. 30-amp two-pole breaker
Show the answer

D. 30-amp two-pole breaker — Match the circuit to the conductor and appliance rating.

Question 2

At what current does a Class A GFCI trip?

  1. About 4–6 mA of ground fault current
  2. About 15 amps, the same as the circuit breaker
  3. About 30 mA
  4. About 1 amp
Show the answer

A. About 4–6 mA of ground fault current — Fast tripping protects people.

Question 3

What is a continuous load?

  1. Any load over 20 A
  2. A load where the maximum current is expected to continue for 3 hours or more
  3. A motor load only
  4. A load running 1 hour
Show the answer

B. A load where the maximum current is expected to continue for 3 hours or more — Lighting in commercial buildings is often continuous.

Question 4

What is the main purpose of an overcurrent device?

  1. To increase voltage
  2. To protect people from shock by tripping at about 5 milliamps
  3. To protect conductors and equipment from excessive current
  4. To ground equipment
Show the answer

C. To protect conductors and equipment from excessive current — GFCIs protect people from shock.

Question 5

When may the next higher standard overcurrent device be used above a conductor's ampacity?

  1. Only for motors
  2. Always
  3. Never
  4. When the conductor's ampacity doesn't match a standard rating and the device is 800 A or less, and it isn't a multi-outlet branch circuit for cord-and-plug loads
Show the answer

D. When the conductor's ampacity doesn't match a standard rating and the device is 800 A or less, and it isn't a multi-outlet branch circuit for cord-and-plug loads — See 240.4(B).

More Journeyman Electrician topics