What is the formula for angular frequency (ω) in an A.C. circuit?
A
ω = 2πf B
ω = f / 2π C
ω = πf D
ω = 2f
Analysis & Theory
Angular frequency is given by ω = 2πf, where f is the frequency.
In an A.C. circuit, the current lags the voltage when the circuit is:
A
Purely resistive B
Purely capacitive C
Purely inductive D
A short circuit
Analysis & Theory
In an inductive circuit, current lags behind voltage by 90°.
Which of the following expressions represents average power in an A.C. circuit?
A
P = VI B
P = V × I × cos(φ) C
P = V × I × sin(φ) D
P = V × I × tan(φ)
Analysis & Theory
Average power in A.C. = V × I × cos(φ), where φ is the phase angle.
What is the unit of reactance?
A
Ohm (Ω) B
Farad (F) C
Henry (H) D
Siemens (S)
Analysis & Theory
Reactance is measured in ohms (Ω), just like resistance.
Impedance (Z) in an A.C. circuit is a combination of:
A
Only resistance B
Only reactance C
Resistance and capacitance D
Resistance and reactance
Analysis & Theory
Impedance is the total opposition to A.C. and includes both resistance and reactance.
What is the power factor of a circuit with purely reactive load?
A
1 B
0 C
0.5 D
Infinity
Analysis & Theory
For a purely reactive circuit (inductive or capacitive), power factor is zero.
Which of the following best defines RMS (Root Mean Square) value?
A
Maximum value of A.C. B
Average of all instantaneous values C
Effective value producing same heating as DC D
Value at peak of sine wave
Analysis & Theory
RMS value gives the equivalent DC value that produces the same heating effect.
In an RLC series circuit at resonance, the impedance is:
A
Maximum B
Minimum C
Zero D
Infinite
Analysis & Theory
At resonance, inductive and capacitive reactances cancel, resulting in minimum impedance.
Which law is used to analyze A.C. circuits just like in D.C. circuits?
A
Coulomb's Law B
Lenz's Law C
Kirchhoff’s Laws D
Faraday’s Law
Analysis & Theory
Kirchhoff’s Current and Voltage Laws apply to both D.C. and A.C. circuits.
The phase angle in a purely resistive A.C. circuit is:
A
0° B
90° C
-90° D
180°
Analysis & Theory
In a resistive circuit, voltage and current are in phase, so phase angle = 0°.