Alternating Current 2

Objective Questions of Electrician and Wireman: Alternating Current 2

Subject: Alternating Current 2

Part 2: Objective questions and answers of Alternating Current

Q1. What is the unit of susceptance?

a) Mho

b) Ohm

c) Henry

Q2. 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

Q3. 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

Q4. 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

Q5. What is the phase displacement in a single phase AC circuit?

a) 90 Degree

b) 120 Degree

c) 180 Degree

d) 270 Degree

Q6. What is the power factor in a 3 phase power measurement of two wattmeter showing equal readings?

a) 0

b) 1

c) 0.5

d) 0.8

Q7. 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

Q8. 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

Q9. 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

Q10. What is the P.F if one of the wattmeter 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

Q11. 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

Q12. 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

Q13. What is the reciprocal of inductance in AC parallel circuit?

a) Reactance

c) Conductance

d) Susceptance

Q14. 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

Q15. 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

Q16. Which quantity is rotating at a constant angular velocity?

a) Scalar quantity

b) Vector quantity

c) Phase quantity

d) Algebraic quantity

Q17. The resistance of an open circuit is equal to:

a) Zero

b) Lesser than one ohm

c) Infinite

d) Lesser than before

Q18. The power dissipation of a pure inductor is:

a) Very low

b) Zero

c) Very high

d) Lesser than unity

Q19. The magnitude of inductance………. With an increase in the frequency.

a) Decreases

b) Remains unchanged

c) Increases

d) Becomes zero

Q20. The difference between peak positive and peak negative values of an A.C. voltage is called:

a) Maximum value

b) Average value

c) Effective value

d) Peak-to-peak value

Part 2: Objective questions and answers of Alternating Current