Licensed Electrical Contractor Code, Theory, and Calculations 5

Question 1

A 120 V circuit has a total resistance of 24 Ω. Using Ohm's Law, what is the current in the circuit?

Accepted Answer

5 A

Answer

I = V ÷ R = 120 ÷ 24 = 5 A.

Question 2

Under NEC Article 220, the general lighting load for a dwelling unit is calculated using a unit load of:

Accepted Answer

3 VA per square foot

Answer

NEC Table 220.12 specifies 3 VA per square foot for the general lighting load in dwelling units.

Question 3

The impedance of a series RLC circuit at resonance is equal to:

Accepted Answer

The resistance R only

Answer

At resonance, XL = XC, so they cancel, and the impedance equals only the resistance R.

Question 4

NEC 230.23 states that service entrance conductors installed as open individual conductors overhead shall not be smaller than:

Accepted Answer

8 AWG copper

Answer

NEC 230.23(A) requires a minimum of 8 AWG copper for overhead service entrance conductors installed as open conductors.

Question 5

What is the apparent power (in kVA) of a 3-phase load drawing 40 A at 480 V?

Accepted Answer

33.3 kVA

Answer

3-phase apparent power S = √3 × VL × IL = 1.732 × 480 × 40 ≈ 33,254 VA ≈ 33.3 kVA.

Licensed Electrical Contractor Practice Test