AC Circuit Questions and Answers pdf - ObjectiveBooks
AC Circuit Questions and Answers pdf

AC Circuit Questions and Answers pdf

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Practice Test: Question Set - 02

1. In which 3 phase system, the artificial neutral is required to measure the phase voltage?
    (A) 3 wire star connected system
    (B) 4 wire star connected system
    (C) 3 wire delta connected system
    (D) 4 wire delta connected system
2. What is the main cause for below 0.5 lagging power factor in 3 phase system?
    (A) Due to fluctuation of voltage
    (B) True power due to resistive load
    (C) Reactive power due to more inductive load
    (D) Reactive power due to more capacitive load
3. Calculate the power factor of coil having resistance of 24 Ohm, draws the current of 5A, at 240V/ 50HZ AC supply.
    (A) 0.8
    (B) 0.6
    (C) 0.5
    (D) 0.3
4. Which electrical term is defined as the total opposition to current in AC parallel circuit?
    (A) Resistance
    (B) Impedance
    (C) Admittance
    (D) Susceptance
5. What is the phase displacement between phases in a 3-phase circuit?
    (A) 90°
    (B) 120°
    (C) 180°
    (D) 360°
6. How the resonance frequency (fr) can be increased in A.C series circuit?
    (A) Increasing the inductance value
    (B) Reducing the capacitance value
    (C) Increasing the capacitance value
    (D) Increasing the value of resistance
7. Calculate the power factor of R.L.C circuit having resistance (R) = 15 Ohm, resultant reactance (X) = 20W connected across 240V /50Hz AC supply?
    (A) 0.5
    (B) 0.6
    (C) 0.7
    (D) 0.8
8. What is the reciprocal of inductance in AC parallel circuit?
    (A) Reactance
    (B) Admittance
    (C) Conductance
    (D) Susceptance
9. What is the current in neutral conductor in 3 phase unbalanced load in star connected system?
    (A) No current will flow
    (B) The algebraic sum of current in 3 phases
    (C) The algebraic sum of current in 2 phases only
    (D) Lesser than the lowest current in any one of the phases
10. Calculate the apparent power of a star connected 3 phase load, if it is connected across 3 phase 415volt/50Hz supply at 0.8 p.f and the phase current is 10 Amps
    (A) 12.45 KVA
    (B) 57.50 KVA
    (C) 3.320 KVA
    (D) 7.188 KVA
11. Calculate the apparent power in KVA of 3 phase 415V, 50 Hz, star system, if the line current (IL) is 16A at 0.8 power factor.
    (A) 15.2 KVA
    (B) 11.5 KVA
    (C) 9.2 KVA
    (D) 5.3 KVA
12. Calculate the total power by two wattmeter (W1 & W2) method, if one of the wattmeter (W2) reading is taken after reversing.
    (A) W1 × 2
    (B) W1 only
    (C) W1 - W2
    (D) W1 + W2
13. Calculate the line current of the 3 phase 415V 50 HZ supply for the balanced load of 3000 watt at 0.8 power factor is connected in star.
    (A) 8.5 A
    (B) 5.2 A
    (C) 4.5 A
    (D) 3.4 A
14. What is the purpose of phase sequence meter?
    (A) To control the speed of 3 phase motor
    (B) To protect motor against short circuit fault
    (C) To indicate the incorrect phase sequence of 3 phase
    (D) To ensure the correct phase sequence of 3 phase system
15. In a 3 phase system, if the active power is 4 kw and the apparent power is 5 KVA, calculate the reactive power?
    (A) 1 KVAR
    (B) 2 KVAR
    (C) 3 KVAR
    (D) 4 KVAR
16. Which condition is called as resonance RLC circuit?
    (A) XL > XC
    (B) XC > XL
    (C) XL = XC
    (D) R < XL
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