1. What is the unit of susceptance?
A Mho
B Ohm
C Henry
D Farad
2. What is the resistance of the inductive coil takes 5A current across 240V, 50Hz supply at 0.8 power factor?
A 48 $\displaystyle \Omega$
B 42.5 $\displaystyle \Omega$
C 38.4 $\displaystyle \Omega$
D 26.6 $\displaystyle \Omega$
3. 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
4. What is the formula to find 3 phase Reactive power (PR) if the line voltage is $\displaystyle V_{L}$ and line current is $\displaystyle I_{L}$?
A $\displaystyle Pr=V_{L}I_{L}$
B $\displaystyle Pr=3V_{L}I_{L}\cos \theta$
C $\displaystyle Pr=\sqrt{3}V_{L}I_{L}\sin \theta$
D $\displaystyle Pr=\sqrt{3}V_{L}I_{L}\cos \theta$
5. 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
6. 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
7. 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
8. 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
9. What is the maximum value of voltage for 240 volt RMS?
A 240V
B 415V
C 339.5V
D 376.8V
10. What is the formula for Reactive Power (Pr) in an AC circuit?
A $\displaystyle Pr=VI$
B $\displaystyle Pr=\sqrt{2}VI$
C $\displaystyle Pr=VI\cos \theta$
D $\displaystyle Pr=VI\sin \theta$
11. Calculate the impedance of the circuit $\displaystyle R=5\Omega$, $\displaystyle X_{L}=36\Omega$ and $\displaystyle X_{C}=24\Omega$
B 65 $\displaystyle \Omega$
C 13 $\displaystyle \Omega$
D 12 $\displaystyle \Omega$
12. What is the phase displacement in a single phase AC circuit?
A 90°
B 120°
C 180°
D 270°
13. What is the relation between the line voltage ($\displaystyle V_{L}$) and phase voltage ($\displaystyle V_{P}$) in star connected system?
A $\displaystyle V_{L}=\sqrt{3}V_{P}$
B $\displaystyle V_{L}=3V_{P}$
C $\displaystyle V_{L}=\frac{V_{P}}{\sqrt{3}}$
D $\displaystyle V_{L}=V_{P}/3$
14. 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
15. 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
16. Calculate the power factor of coil having resistance of 24$\displaystyle \Omega$, draws the current of 5A, at 240V/50HZ AC supply
A 0.8
B 0.6
C 0.5
D 0.3
17. What is the formula to calculate the impedance (Z) of the R.L.C series circuit, if the inductive reactance ($\displaystyle X_{L}$) is less than capacitive reactance ($\displaystyle X_{C}$)?
A $\displaystyle Z=R^{2}+\sqrt{X_{L}^{2}+X_{C}^{2}}$
B $\displaystyle Z=\sqrt{R^{2}+(X_{L}-X_{C})^{2}}$
C $\displaystyle Z=\sqrt{R^{2}+(X_{L}^{2}-X_{C})^{2}}$
D $\displaystyle Z=\sqrt{R^{2}+(X_{C}-X_{L})^{2}}$
18. Calculate the power factor of R.L.C circuit having resistance (R) = 15$\displaystyle \Omega$ , resultant reactance (X) = 20$\displaystyle \Omega$ connected across 240V /50Hz AC supply?
A 0.5
B 0.6
C 0.7
D 0.8
19. 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
20. What is the formula to calculate the line current ($\displaystyle I_{L}$) of this single phase R - C parallel circuit?
B $\displaystyle I_{L}=I_{R}+I_{C}$
C $\displaystyle I_{L}=I_{R}^{2}-I_{C}^{2}$
D $\displaystyle I_{L}=\sqrt{I_{R}^{2}-I_{C}^{2}}$
21. 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
22. What is the relation between the line current ($\displaystyle I_{L}$) and phase current ($\displaystyle I_{P}$) in delta connected system?
A $\displaystyle I_{L}=I_{P}$
B $\displaystyle I_{L}=3I_{P}$
C $\displaystyle I_{L}=\sqrt{3}I_{P}$
D $\displaystyle I_{L}=I_{P}/\sqrt{3}$
23. 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
24. 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
25. 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
26. What is the formula for form factor(Kf)?
A $\displaystyle K_{f}=\frac{Average\: Value}{RMS\: Value}$
B $\displaystyle K_{f}=\frac{RMS\: Value}{Average\: Value}$
C $\displaystyle K_{f}=\frac{Maximum\: Value}{Average\: Value}$
D $\displaystyle K_{f}=\frac{RMS\: Value}{Maximum\: Value}$
27. Which electrical term is defined as the total opposition to current in AC parallel circuit?
A Resistance
B Impedance
C Admittance
D Susceptance
28. Which AC circuit contains the phase relation between voltage (V) and current (I)?
B Resistance and inductance circuit
C Resistance and capacitance circuit
D Resistance, inductance and capacitance circuit
29. 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
30. In which condition resonance will occur in R-L-C 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)
31. 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
32. What is the form factor (Kf) for sinusoidal AC?
A 1
B 1.11
C 2.22
D 4.44
33. What is the reciprocal of inductance in AC parallel circuit?
A Reactance
B Admittance
C Conductance
D Susceptance
34. What relationship is illustrated in between the current and voltage?
B Current and voltage are in out of phase
C Current lags behind the voltage
D Current leads ahead of the voltage
35. Calculate the total power by two wattmeter (W1 & W2) method, if one of the wattmeter (W2) reading is taken after reversing.
A W1 x 2
B W1 only
C W1 - W2
D W1 + W2
36. 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
37. 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
38. Which formula is used to calculate Form factor (Kf)?
A $\displaystyle K_{f}=\frac{Effective\: Value}{Average\: Value}$
B $\displaystyle K_{f}=\frac{Average\: Value}{Effective\: Value}$
C $\displaystyle K_{f}=\frac{Effective\: Value}{Maximum\: Value}$
D $\displaystyle K_{f}=\frac{Average\: Value}{Maximum\: Value}$
39. Which formula is used to calculate the impedance (z) of a RLC series circuit?
A $\displaystyle Z=R^{2}+(X_{L}-X_{C})^{2}$
B $\displaystyle Z=\sqrt{R^{2}+(X_{L}-X_{C})}$
C $\displaystyle Z=\sqrt{R+(X_{L}^{2}-X_{C})}$
D $\displaystyle Z=\sqrt{R^{2}+(X_{C}-X_{L})^{2}}$
40. 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
41. What is the phase displacement between phases in a 3-phase circuit?
A 90°
B 120°
C 180°
D 360°
42. Which condition is called as resonance RLC circuit ?
A $\displaystyle X_{L}>X_{C}$
B $\displaystyle X_{C}>X_{L}$
C $\displaystyle X_{L}=X_{C}$
D $\displaystyle R<X_{L}$
43. Which quantity is rotating at a constant angular velocity?
A Scalar quantity
B Vector quantity
C Phasor quantity
D Algebraic quantity
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