Licensed Electrical Contractor Electrical Theory & Fundamentals 5

Question 1

What is the purpose of a transformer in an electrical distribution system?

Accepted Answer

Step voltage up or down while transferring power

Answer

A transformer uses electromagnetic induction to step voltage up or down, allowing efficient long-distance power transmission and distribution at appropriate voltages.

Question 2

What is 'skin effect' in AC conductors?

Accepted Answer

Tendency of AC current to flow near the outer surface of a conductor

Answer

Skin effect causes high-frequency AC current to concentrate near the conductor's outer surface, effectively reducing the usable cross-sectional area and increasing resistance.

Question 3

What is the formula for capacitive reactance (XC)?

Accepted Answer

XC = 1 / (2πfC)

Answer

Capacitive reactance XC = 1/(2πfC), showing that it decreases as frequency or capacitance increases.

Question 4

Three 6-ohm resistors are connected in series. What is the total resistance?

Accepted Answer

18 ohms

Answer

Series resistors add directly: R_total = 6 + 6 + 6 = 18 ohms.

Question 5

What is the significance of the power triangle in AC circuit analysis?

Accepted Answer

It shows the relationship between apparent power, true power, and reactive power

Answer

The power triangle uses the Pythagorean theorem to relate apparent power (S), true/real power (P), and reactive power (Q): S² = P² + Q².

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Electrical Theory & Fundamentals 5