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

A. Voltage

B. Resistance

C. Impedance

D. 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})

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

54. 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

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

A. sinusoidal

B. square

C. constant

D. triangular

56. What is not a frequency for ac current?

A. 50 Hz

B. 55 Hz

C. 0Hz

D. 60 Hz

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

A. sinusoidal

B. triangular

C. square

D. complex waveform