NEC General Electrical Theory & Code Definitions 3 — Questions and Answers
Question 1: What is the NEC definition of 'ground fault'?
- An intentional connection between a circuit conductor and earth
- An unintentional, electrically conducting connection between an ungrounded conductor and a normally non-current-carrying conductor or conductive material (Correct answer)
- A fault between two ungrounded conductors
- A break in the grounding electrode conductor
Correct answer: An unintentional, electrically conducting connection between an ungrounded conductor and a normally non-current-carrying conductor or conductive material
NEC Article 100 defines a ground fault as an unintentional, electrically conducting connection between an ungrounded conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, or earth.
Question 2: Which law states that the total power in an electrical circuit equals the sum of the powers consumed by each element?
- Ohm's Law
- Kirchhoff's Voltage Law
- Kirchhoff's Current Law
- Watt's Law (Conservation of Energy) (Correct answer)
Correct answer: Watt's Law (Conservation of Energy)
The conservation of energy principle (Watt's Law) states that total power supplied to a circuit equals the sum of the power consumed by all individual elements.
Question 3: According to the NEC, what is an 'authority having jurisdiction' (AHJ)?
- The electrical contractor on a job
- An organization, office, or individual responsible for enforcing the requirements of a code (Correct answer)
- The National Fire Protection Association
- A licensed master electrician
Correct answer: An organization, office, or individual responsible for enforcing the requirements of a code
NEC Article 100 defines AHJ as an organization, office, or individual responsible for enforcing the requirements of a code or standard, or their designated representative.
Question 4: In AC circuits, what does 'power factor' represent?
- The ratio of true power to apparent power (Correct answer)
- The ratio of voltage to current
- The efficiency of the transformer
- The percentage of voltage drop in the circuit
Correct answer: The ratio of true power to apparent power
Power factor is the ratio of true (real) power in watts to apparent power in volt-amperes, representing how effectively electrical power is being used.
Question 5: What is the NEC definition of a 'receptacle'?
- Any device used to connect equipment to a circuit
- A contact device installed at the outlet for the connection of an attachment plug (Correct answer)
- A box that contains wiring connections
- A device used to terminate conductors
Correct answer: A contact device installed at the outlet for the connection of an attachment plug
NEC Article 100 defines a receptacle as a contact device installed at the outlet for the connection of an attachment plug, or for the direct connection of electrical utilization equipment.
Question 6: For a purely resistive AC circuit, how does the phase relationship between voltage and current appear?
- Current leads voltage by 90°
- Voltage leads current by 90°
- Voltage and current are in phase (0° difference) (Correct answer)
- Current lags voltage by 45°
Correct answer: Voltage and current are in phase (0° difference)
In a purely resistive circuit, voltage and current are in phase with each other, meaning they reach their peak and zero values at the same time.
Question 7: What does the NEC term 'accessible (as applied to wiring methods)' mean?
- Capable of being removed or exposed without damaging the building structure (Correct answer)
- Having a clear working space of at least 3 feet
- Reachable without the use of a ladder
- Located within 6 feet of the floor
Correct answer: Capable of being removed or exposed without damaging the building structure
Per NEC Article 100, accessible as applied to wiring methods means capable of being removed or exposed without damaging the building structure or finish, or not permanently closed in by the structure.
NEC General Electrical Theory & Code Definitions 3
What is the NEC definition of 'ground fault'?