CEA NEC Code and Calculations Questions and Answers

Question 1

An apprentice is installing a 4" x 4" x 1-1/2" square metal box.
The box will contain two duplex receptacles and will have six 12 AWG THHN conductors and two 14 AWG THHN conductors passing through without being spliced or terminated.
According to the NEC, what is the minimum required volume for this box?

Accepted Answer

30.3 cubic inches

Answer

21.0 cubic inches

Answer

27.0 cubic inches

Answer

31.5 cubic inches

Question 2

Which of the following is the primary reason for applying an ampacity adjustment factor when more than three current-carrying conductors are bundled together in a raceway for a continuous length?

Accepted Answer

To manage the heat generated by the conductors in a confined space.

Answer

To account for voltage drop over the length of the conductor.

Answer

To compensate for the increased magnetic fields from adjacent conductors.

Answer

To ensure the overcurrent protection device operates correctly.

Question 3

An apprentice needs to calculate the minimum size THWN copper branch-circuit conductors for a 7.5 horsepower, 230-volt, 3-phase motor with a nameplate full-load current (FLC) of 22 amperes. The motor is on a continuous duty cycle. What is the minimum required ampacity for the conductors?

Accepted Answer

27.5 amperes

Answer

22 amperes

Answer

24.2 amperes

Answer

30 amperes

Question 4

A single-family dwelling has a calculated general lighting and receptacle load of 18,000 VA. According to the standard calculation method in NEC Article 220, what is the demand load that should be used for sizing the service?

Accepted Answer

9,300 VA

Answer

18,000 VA

Answer

10,800 VA

Answer

6,300 VA

Question 5

What is the maximum number of 12 AWG THHN conductors that can be installed in a 1/2-inch Electrical Metallic Tubing (EMT) conduit?

Accepted Answer

9

Answer

7

Answer

12

Answer

16

Question 6

An apprentice is tasked with calculating the voltage drop for a 120V single-phase circuit. The circuit is 150 feet long one-way and carries a load of 16 amps using 12 AWG solid copper conductors. What is the approximate voltage drop? (Use K=12.9 for copper)

Accepted Answer

7.4 volts

Answer

3.7 volts

Answer

5.9 volts

Answer

9.3 volts