NECA Electrical Theory & Principles 3

Question 1

What is the phase relationship between voltage and current in a purely capacitive AC circuit?

Accepted Answer

Current leads voltage by 90°

Answer

In a purely capacitive circuit, current leads voltage by 90° because the capacitor must charge before a voltage develops across it.

Question 2

Which of the following best describes electric potential difference (voltage)?

Accepted Answer

The work done per unit charge to move charge between two points

Answer

Voltage (potential difference) is defined as the work done per unit charge (W/Q) required to move a charge between two points in an electric field.

Question 3

A 120V circuit has a load drawing 15A. What is the power consumed?

Accepted Answer

1,800 W

Answer

Power P = V × I = 120 V × 15 A = 1,800 W (1.8 kW).

Question 4

In a series RLC circuit at resonance, the impedance is:

Accepted Answer

Minimum and equal to resistance only

Answer

At resonance, inductive reactance equals capacitive reactance and they cancel, leaving only resistance — making impedance minimum and purely resistive.

Question 5

The skin effect in conductors causes high-frequency AC current to:

Accepted Answer

Concentrate near the outer surface

Answer

The skin effect causes AC current at higher frequencies to flow primarily near the conductor's surface, effectively reducing the useful cross-sectional area and increasing resistance.

(NECA) National Electrical Contractors Association Practice Test

(NECA) National Electrical Contractors Association Practice Test

NECA Electrical Theory & Principles 3