# Alternating Current RLC Circuit MCQ [Free PDF] – Objective Question Answer for Alternating Current RLC Circuit Quiz

1. Find the total voltage applied in a series RLC circuit when i = 3mA, VL = 30V, VC = 18V, and R = 1000 ohms.

A. 3.95V
B. 51V
C. 32.67V
D. 6.67V

Total voltage = VR+VL+VC.

VR = 1000 × 3 × 10-3 = 3V.

Therefore, total voltage = 30+18+3 = 51V.

2. In an RLC circuit, which of the following is always used as a vector reference?

A. Voltage
B. Resistance
C. Impedance
D. Current

In an RLC circuit, the voltage is always used as a reference and according to the phase of the voltage, the phase of the other parameters is decided.

3. In an RLC circuit, the power factor is always ____________

A. Positive
B. Negative
C. Depends on the circuit
D. Zero

In an RLC series circuit, the power factor depends on the number of resistors and inductors in the circuit, hence it depends on the circuit.

4. In an RLC series phasor, we start drawing the phasor from which quantity?

A. Voltage
B. Resistance
C. Impedance
D. Current

In an RLC series phasor diagram, we start drawing the phasor from the quantity which is common to all three components, that is the current.

5. What is the correct expression for the phase angle in an RLC series circuit?

A. φ = tan-1(XL-XC)/R
B. φ = tan-1 (XL+XC)/R
C. φ = tan(XL-XC)/R
D. φ = tan-1 (XL-XC)

From the impedance triangle, we get

tanφ = (XL-XC)/R.

Hence φ = tan-1 (XL-XC)/R.

6. When is tanφ positive?

A. When inductive reactance is less than the capacitive reactance
B. When inductive reactance is greater than the capacitive reactance
C. When inductive reactance is equal to capacitive reactance
D. When inductive reactance is zero

tanφ is positive when inductive reactance is greater than capacitive reactance because current will lag the voltage.

7. When is tanφ negative?

A. When inductive reactance is less than the capacitive reactance
B. When inductive reactance is greater than the capacitive reactance
C. When inductive reactance is equal to capacitive reactance
D. When inductive reactance is zero

tanφ is negative when inductive reactance is less than capacitive reactance because current will lead to the voltage.

8. Which of the following is not an ac waveform?

A. sinusoidal
B. square
C. constant
D. triangular

AC waveforms are those which periodically change polarity with time. Sinusoidal waves, square waves, and triangular wave change their polarity at regular intervals so they are ac waveforms. A constant wave doesn’t change its polarity so it is not an ac waveform.

9. What is not a frequency for ac current?

A. 50 Hz
B. 55 Hz
C. 0Hz
D. 60 Hz

DC current is a type of constant current so it has a frequency of zero hertz. So, AC current can have rest other frequencies other than zero.

10. Which type of ac waveform is shown in the given figure?

A. sinusoidal
B. triangular
C. square
D. complex waveform