Licensed Electrical Contractor Code, Theory, and Calculations 2

Question 1

According to NEC Article 310, what is the ampacity of a 12 AWG copper conductor with THHN insulation installed in a conduit with an ambient temperature of 30°C?

Accepted Answer

30 A

Answer

A 12 AWG copper THHN conductor has a base ampacity of 30 A at 75°C column per NEC Table 310.15(B)(16), with no correction needed at 30°C ambient.

Question 2

When applying the NEC demand factor for household electric dryers in a multifamily building with 20 dryers, what demand factor applies per Table 220.54?

Accepted Answer

35%

Answer

NEC Table 220.54 assigns a 35% demand factor for 20 household electric dryers in a multifamily dwelling.

Question 3

Kirchhoff's Voltage Law (KVL) states that the algebraic sum of all voltages around any closed loop equals:

Accepted Answer

Zero

Answer

KVL states that the sum of all voltage rises and drops around any closed loop is zero, reflecting conservation of energy.

Question 4

A 240 V single-phase motor draws 18 A at a power factor of 0.85. What is the true (real) power consumed?

Accepted Answer

3,672 W

Answer

True power P = V × I × PF = 240 × 18 × 0.85 = 3,672 W.

Question 5

Under NEC 230.70, the service disconnecting means must be located:

Accepted Answer

Inside the building as close as practicable to the point of service entry

Answer

NEC 230.70 requires the service disconnect to be inside or outside the building nearest the point where the service conductors enter.

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Code, Theory, and Calculations 2