AC Circuit Analysis: Master Impedance, Phase Angle, and Power Factor

Question 1

In an AC circuit, the voltage V = 100V and the current I = 5A. What is the phase angle (θ) if the voltage leads the current by 30 degrees?

Accepted Answer

30 degrees

Answer

60 degrees

Answer

90 degrees

Answer

120 degrees

Question 2

Which of the following is NOT a type of AC motor?

Accepted Answer

DC motor

Answer

Induction motor

Answer

Synchronous motor

Answer

Stepper motor

Question 3

Which of the following does NOT affect the resonant frequency of a circuit?

Accepted Answer

Voltage of the supply

Answer

Inductance

Answer

Capacitance

Answer

Resistance

Question 4

In an AC circuit, what is the relationship between impedance (Z), resistance (R), inductance (L), and capacitance (C)?

Accepted Answer

Z = R + j(XL - XC)

Answer

Z = R - j(XL - XC)

Answer

Z = j(XL + XC)

Answer

Z = R + j(XL + XC)

Question 5

What is resonance in AC circuits?

Accepted Answer

Condition when inductive reactance equals capacitive reactance

Answer

Condition when inductive reactance exceeds capacitive reactance

Answer

Condition when capacitive reactance exceeds inductive reactance

Answer

Condition when impedance is maximum

Question 6

What is the Q-factor of an AC circuit?

Accepted Answer

Measure of the circuit's resonant frequency selectivity

Answer

Measure of the circuit's efficiency

Answer

Measure of the circuit's power factor

Answer

Measure of the circuit's bandwidth

Question 7

Which of the following is NOT an application of AC circuit analysis?

Accepted Answer

Electroplating

Answer

Power transmission and distribution

Answer

Audio amplifiers

Answer

Radio frequency communication

Question 8

What is the primary advantage of using AC over DC in power transmission?

Accepted Answer

Lower voltage drop over long distances due to lower resistance

Answer

Higher current carrying capacity of AC wires

Answer

Improved power quality

Answer

Reduced electromagnetic interference

Question 9

What type of filter can be used to allow low-frequency signals to pass through while blocking high-frequency signals?

Accepted Answer

Low-pass filter

Answer

High-pass filter

Answer

Band-pass filter

Answer

Band-stop filter

Question 10

In an AC circuit with resistance (R), inductance (L), and capacitance (C) connected in series, what formula accurately calculates the impedance (Z)?

Accepted Answer

Z = R + j(XL - XC)

Answer

Z = R + √(XL² - XC²)

Answer

Z = R - j(XL - XC)

Answer

Z = R - √(XL² - XC²)

Question 11

What is the primary purpose of using a power factor correction capacitor in an AC circuit?

Accepted Answer

To enhance the power factor

Answer

To diminish the power factor

Answer

To increase the current flow

Answer

To decrease the voltage level

Question 12

Which condition signifies resonance in an AC circuit?

Accepted Answer

XL = XC

Answer

XL ≠ XC

Answer

Z = 0

Answer

Z = ∞

Question 13

How does increasing the frequency of an AC source affect the inductive reactance (XL) of an inductive circuit?

Accepted Answer

Increases XL

Answer

Decreases XL

Answer

Has no effect on XL

Answer

Reverses XL

Question 14

What is the unit of measurement for capacitive reactance (XC)?

Accepted Answer

Ohms

Answer

Volts

Answer

Henrys

Answer

Farads

Question 15

Which statement about AC circuits is incorrect?

Accepted Answer

AC circuits are exclusively high-frequency circuits.

Answer

Voltage and current can be in phase with each other.

Answer

Inductors store energy in a magnetic field.

Answer

Capacitors store energy in an electric field.

Question 16

Determine the phase angle between voltage and current in a purely capacitive circuit.

Accepted Answer

-90° leading

Answer

0°

Answer

-90° lagging

Answer

180°

Question 17

Calculate the impedance of an AC circuit with a resistance of 10 Ω, an inductive reactance of 5 Ω, and a capacitive reactance of 3 Ω.

Accepted Answer

8.06 Ω

Answer

2.06 Ω

Answer

13 Ω

Answer

18 Ω

Question 18

Determine the power factor in a purely resistive circuit.

Accepted Answer

1

Answer

0.5

Answer

-1

Answer

0

Question 19

Identify the condition that represents resonance in an AC circuit.

Accepted Answer

XL = XC

Answer

XL > XC

Answer

R > XL + XC

Answer

XL < XC

Question 20

Determine the current at resonance in an AC circuit.

Accepted Answer

Maximum

Answer

Minimum

Answer

Equal to the source voltage

Answer

Zero

Question 21

Identify the factors that affect the resonant frequency of an AC circuit.

Accepted Answer

Inductance and capacitance

Answer

Inductance only

Answer

Resistance only

Answer

Capacitance only

Question 22

Which type of filter circuit passes low-frequency signals while blocking high-frequency signals?

Accepted Answer

Low-pass filter

Answer

High-pass filter

Answer

Band-stop filter

Answer

Band-pass filter