CME NEC Code and Theory Questions and Answers

Question 1

According to NEC Article 500, which of the following best describes a Class I, Division 1 hazardous location?

Accepted Answer

A location in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitible mixtures under normal operating conditions.

Answer

A location where ignitible fibers or flyings are handled, manufactured, or used.

Answer

A location where combustible dust is normally in suspension in the air in quantities sufficient to produce explosive or ignitible mixtures.

Answer

A location where volatile flammable liquids or flammable gases are handled, but are normally confined within closed containers from which they can escape only in case of accidental rupture.

Question 2

A 480V to 208Y/120V, 75 kVA transformer is installed indoors to create a new separately derived system. Per NEC 250.30(A), where must the system bonding jumper be installed?

Accepted Answer

At either the source of the separately derived system or at the first system disconnecting means, but not at both locations.

Answer

Only at the transformer's secondary neutral terminal.

Answer

At both the transformer and the first disconnecting means.

Answer

Only within the enclosure for the first system disconnecting means or switchboard.

Question 3

An electrician is installing three sets of 500 kcmil THWN copper conductors in parallel for a 3-phase, 4-wire feeder. Which of the following is NOT a requirement for this parallel installation according to NEC 310.10?

Accepted Answer

Each parallel conductor must have its own separate equipment grounding conductor.

Answer

All conductors must be the same length.

Answer

All conductors must be made of the same material.

Answer

All conductors must have the same circular mil area and insulation type.

Question 4

A 400A feeder is protected by a 400A circuit breaker. Under the '25-foot tap rule' in NEC 240.21(B)(2), what is the minimum required ampacity for the tap conductors?

Accepted Answer

133A

Answer

100A

Answer

40A

Answer

200A

Question 5

When grounding an indoor separately derived AC system, such as a dry-type transformer, which of the following must be used as the grounding electrode?

Accepted Answer

The building or structure grounding electrode system.

Answer

The nearest available qualified metal water pipe.

Answer

A new ground rod driven at the transformer location.

Answer

The metal frame of the building, if effectively grounded.

Question 6

Which of the following conditions would classify a location as Class II, Division 1 according to the NEC?

Accepted Answer

Where combustible dust is in the air under normal operating conditions in quantities sufficient to produce explosive or ignitible mixtures.

Answer

Where ignitible concentrations of flammable gases can exist under normal operating conditions.

Answer

Where easily ignitible fibers are stored or handled, but not in the process of manufacture.

Answer

Where combustible dust is not normally in the air but may be present as a result of infrequent malfunctioning of handling equipment.