Lineman Electrical Theory and Principles 3

Question 1

In a balanced three-phase system, what is the phase angle difference between each phase?

Accepted Answer

120 degrees

Answer

In a three-phase system, the three voltage waveforms are separated by 120 degrees (360° ÷ 3) to achieve balanced power delivery.

Question 2

What is the line voltage in a three-phase wye (Y) system if the phase voltage is 7,200V?

Accepted Answer

12,470V

Answer

In a wye system, line voltage = phase voltage × √3, so 7,200V × 1.732 ≈ 12,470V.

Question 3

Capacitive reactance (XC) in an AC circuit behaves how as frequency increases?

Accepted Answer

Decreases inversely

Answer

Capacitive reactance XC = 1/(2πfC), so it decreases as frequency increases — the opposite behavior from inductive reactance.

Question 4

Faraday's Law of Electromagnetic Induction states that the induced EMF in a conductor is proportional to:

Accepted Answer

The rate of change of magnetic flux through the circuit

Answer

Faraday's Law states that induced EMF equals the rate of change of magnetic flux linkage, which is the basis for transformer and generator operation.

Question 5

In AC power systems, what does the term 'impedance' represent?

Accepted Answer

The combined opposition to AC current including resistance and reactance

Answer

Impedance (Z) is the total opposition to AC current flow, combining resistance (R) and reactance (X) using the formula Z = √(R² + X²).

(Lineman) Lineman Certification Practice Test