Free Journeyman Electrician’s General Questions and Answers

Question 1

Conductors with marks on the insulation are NOT approved for use in a wet location.

Accepted Answer

THHN

Answer

Table 310.104(A) shows that conductors with THHN insulation are approved for use in dry and damp locations only, and conductors with THWN, THHW, and THW insulation are recognized for service in dry and wet areas.

Question 2

Given: A one-family dwelling unit with a demand load of 200 amperes is supplied with a 120/240 volt, single-phase electrical system from the local utility company. What are the MINIMUM size aluminium THW conductors required for use as service-entrance conductors for this residence?

Accepted Answer

4/0 AWG

Answer

Section 310.15(B)(7)(1) permits one-family dwelling 120/240 volt, single-phase, service-entrance conductors to be sized at an ampacity of not less than 83% of the service rating.

Therefore, 200 amperes x 83% = 166 amperes

Aluminium conductors of size 4/0 AWG THW with a permissible ampacity of 180 amperes should be chosen for this residence, according to Table 310.15(B)(16).

Question 3

Where a 150 kVA, a single-phase transformer with a secondary voltage of 120/240, is installed at a multi-family dwelling, the secondary's full-load current rating, in amperes, is ___.

Accepted Answer

625 amperes

Answer

To find the full-load current rating of the single-phase transformer apply the single-phase current formula as shown:

I = (150 kVA x 1000) / 240 volts = 15,000/240 = 625 amperes

Question 4

Which circuit breakers mentioned below do NOT have a conventional ampere rating?

Accepted Answer

75 amperes

Answer

Table 240.6(A) illustrates the standard ampere ratings for fuses and circuit breakers. A circuit breaker with an ampere rating of 75 amperes is not a common ampere rating.

Question 5

The MINIMUM length of the free conductor to be left at each junction box for splicing conductors or making connections to luminaires or devices shall be ____ .

Accepted Answer

6 inches

Answer

According to Section 300.14, each junction box must have at least 6 inches of open conductors available for splices or connecting luminaires or other devices. This guideline aims to ensure enough conductor slack for the terminal connections or splices to be made easily.

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Practice Test

Free Journeyman Electrician’s General Questions and Answers