Licensed Electrical Contractor FREE Licensed Electrical Contractor Code, Theory, and Calculations Questions and Answers 3

Question 1

What is the standard unit load per square foot used for general lighting in office buildings per the NEC?

Accepted Answer

3.5 VA

Answer

NEC Table 220.12 specifies a unit load of 3.5 VA per square foot for general lighting in office buildings.

Question 2

How many current-carrying conductors can occupy a single conduit before derating factors must be applied per the NEC?

Accepted Answer

3

Answer

Ampacity adjustment factors from NEC Table 310.15(C)(1) apply when more than 3 current-carrying conductors are in a single raceway.

Question 3

What is the power factor of a purely resistive AC circuit?

Accepted Answer

1.0

Answer

A purely resistive AC circuit has a power factor of 1.0 because voltage and current are perfectly in phase.

Question 4

Per the NEC, what is the minimum height above a rooftop for service drop conductors with a roof slope greater than 4 inches in 12 inches?

Accepted Answer

3 feet

Answer

NEC 230.24(A) permits a reduction to 3 feet of clearance above a roof with a slope greater than 4 inches in 12 inches.

Question 5

What is the total impedance of a series RLC circuit with R = 30 ohms, XL = 50 ohms, and XC = 10 ohms?

Accepted Answer

50 ohms

Answer

Total impedance is calculated as Z = sqrt(R² + (XL - XC)²) = sqrt(900 + 1600) = 50 ohms.

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