AC Circuit MCQ Questions and Answers - ObjectiveBooks

# Practice Test: Question Set - 01

1. In which condition resonance will occur in R-LC series circuit?
(A) Inductive reactance (XL) is zero
(B) Inductive reactance (XL) is equal to capacitive reactance (XC)
(C) Inductive reactance (XL) is greater than capacitive reactance (XC)
(D) Inductive reactance (XL) is less than capacitive reactance (XC)

2. What will be the readings of two watt meters (W1& W2) in 3 phase power measurement, if the power factor is zero?
(A) W1 & W2 both are positive reading
(B) W1 is Positive and W2 is negative reading
(C) W1 is equal to W2 but with opposite signs
(D) Zero W1 is Positive reading, and W2 is negative reading

3. Calculate the value admittance (Y) of the RLC parallel circuit connected across 240volts/50Hz AC supply and 8 Amp. Current is passed through it?
(A) 3.33 Mho
(B) 0.33 Mho
(C) 0.033 Mho
(D) 0.003 Mho

4. What is the line voltage in 3 phase system if the phase voltage is 240V?
(A) 380 Volt
(B) 400 Volt
(C) 415 Volt
(D) 440 Volt

5. Which quantity is rotating at a constant angular velocity?
(A) Scalar quantity
(B) Vector quantity
(C) Phasor quantity
(D) Algebraic quantity

6. What is the resistance of the inductive coil takes 5A current across 240V, 50Hz supply at 0.8 power factor?
(A) 48 Ohm
(B) 42.5 Ohm
(C) 38.4 Ohm
(D) 26.6 Ohm

7. What is the maximum value of voltage for 240 volt RMS?
(A) 240 V
(B) 415 V
(C) 339.5 V
(D) 376.8 V

8. What is the power factor in a 3 phase power measurement of two wattmeters showing equal readings?
(A) 0
(B) 1
(C) 0.5
(D) 0.8

9. What is the P.F if one of the wattmeters reading is zero and the other reads total power in 2 wattmeter method of 3 phase power measurement?
(A) 0.5
(B) Zero
(C) Unity
(D) Below 0.5

10. What is the form factor (Kf) for sinusoidal AC?
(A) 1
(B) 1.11
(C) 2.22
(D) 4.44

11. What is the power factor if one of the wattmeter gives negative reading in two wattmeter method of 3 phase power measurement?
(A) 0
(B) 0.5
(C) Unity
(D) Less than 0.5

12. What is the unit of susceptance?
(A) Mho
(B) Ohm
(C) Henry

13. What is the phase displacement in a single phase AC circuit?
(A) 90°
(B) 120°
(C) 180°
(D) 270°

14. How the low power factor (P.F) can be improved in AC circuits?
(A) By connecting resistors in series
(B) By connecting capacitors in series
(C) By connecting inductors in series
(D) By connecting capacitors in parallel

15. How will you obtain positive reading in the wattmeter reads negative reading during 3- phase two wattmeter method?
(A) By interchanging the connections of input terminals
(B) By disconnecting the connection of current coil in meter
(C) By reversing the connection of pressure coil in meter
(D) By reversing the pressure coil and current coil connection in meter

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