CET AC Circuit Analysis & Power 4

Question 1

In a three-phase balanced system, what is the phase voltage if the line voltage is 208 V?

Accepted Answer

120 V

Answer

Phase voltage = Line voltage / √3 = 208 / 1.732 ≈ 120 V in a wye (Y) configuration.

Question 2

What does a leading power factor indicate about a circuit's load?

Accepted Answer

The load is predominantly capacitive

Answer

A leading power factor means current leads voltage, which is the characteristic behavior of a predominantly capacitive load.

Question 3

What is the formula for inductive reactance (XL)?

Accepted Answer

XL = 2πfL

Answer

Inductive reactance XL = 2πfL, where f is frequency in Hz and L is inductance in henries.

Question 4

A 10 Ω resistor and a 10 Ω inductive reactance are connected in series. What is the circuit's power factor?

Accepted Answer

0.707

Answer

PF = cos(θ) = R/Z = 10/√(10²+10²) = 10/14.14 ≈ 0.707.

Question 5

In AC circuit analysis, what does the imaginary component of an impedance phasor represent?

Accepted Answer

Net reactance (inductive or capacitive)

Answer

The imaginary component of impedance (jX) represents net reactance, either inductive (+jX) or capacitive (−jX).

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