Single Phase Series Circuit MCQ [Free PDF] - Objective Question Answer for Single Phase Series Circuit Quiz

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

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

Answer: D

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.

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

A. φ = tan^-1(X_L-X_C)/R
B. φ = tan^-1 (X_L+X_C)/R
C. φ = tan(X_L-X_C)/R
D. φ = tan^-1 (X_L-X_C)

Answer: A

From the impedance triangle, we get

tanφ = (X_L-X_C)/R.

Hence φ = tan^-1 (X_L-X_C)/R.

53. 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

Answer: B

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

54. When is tanφ negative?

Answer: A

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

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

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

Answer: C

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.

56. What is not a frequency for ac current?

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

Answer: C

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.

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