1. DC output is small due to the diode utilized only one half of transformer secondary in ______ in rectifier.
- Half
- Centre – tap
- Bridge
- Full wave
Ans. b
2. Output of bridge rectifier is as those of the centre tap circuit.
- Same
- Twice
- Half
- Four times
Ans. b
3. ______ have universal input.
- UPS
- Rectifier
- regulators
- SMPS
Ans. d
4. On-line UPS is also called as
- Power conditioner
- Line conditioner
- Line interactive UPS
- All the above
Ans. d
5. For an ac input and dc output SMPS, first job is to
- Inversion
- transformation
c. regulation
d. Rectification
Ans. d
6. SMPS in personal computers work with the rated voltage from
- 10kV to 240kV
- 10V to 240V
- 100V to 240V
- 100kV to 240kV
Ans. c
7. Ripple factor of half wave rectifier is
a. 1.11
b. 1.21
c. 1.31
d. 1.4
Ans b
8. Ripple factor of full wave rectifier is
a. 1.11
b. 0.48
c. 0.38
d. 1.4
Ans:b
9The lagging power factor of an ac circuit implies that
(a) the current is lagging the applied voltage
(b) the applied voltage is lagging the current
(c) Both current and applied voltage are in phase
(d) None of the about
Ans : a
10. The current in a resistor circuit
(a) Lags the applied voltage
(b) Leads the applied voltage
(c) Is in phase with the applied voltage
(d) None of these
Ans : c
11. The expression for frequency of ac wave can be represented in terms of no of poles P and its speed N by
(a) 120 PN
(b) 120/ PN
(c) PN/120
(d) 120 P/N
Ans : c
12. Two current wave shapes are represented by i1 = Imax sin wt,
i2 = Imax sin (wt + 30). The current wave i1 is
(a) Lagging the current wave i2 by 30 degree
(b) Lagging the current wave i2 by 30 degree
(c) In phase with current wave i2
(d) None of these
Ans : a
13. The leading power factor of ac circuit implies that,
(a) The current leads the applied voltage
(b The current leads the applied voltage
(c) Current and voltage are in phase
(d) None of these
Ans : a
14. The peak value of voltage of full wave rectified sine wave is 300 V, when measured
by a moving iron voltmeter, its value will be
(a) 300 V
(b) 150 V
(c) 95.4 V
(d) None of these
Ans : b
15. A capacitive circuit of 50 µF and of negligible resistance is connected across a
300 V, 50 Hz single phase supply. The rms value of current drawn by the circuit is
(a) 4. 72 A
(b) 6 A
(c) 16. 68 A
(d) 59. 44 A
Ans : a
16. The overall circuit power factor of a RLC series circuit is found to be 0.898 lagging.
the nature of the resultant circuit is
(a) Resistive
(b) Inductive
(c) Capacitive
(d) None of these
Ans : b
17. The term admittance of ac circuit implies
(a) Reciprocal reactance
(b) Reciprocal impedance
(c) Reciprocal resistance
(d) None of these
Ans : b
18. The effect of fringing
(a) Increases the effective gap area
(b) Decreases the effective gap area
(c) Flux density in air gap is constant
(d) None of these
Ans : a
19. Reason for the induction of emf in a circuit is given by
(a) Fleming’s rule
(b) Lenz’s law
(c) Faraday’s first law
(d) Faraday’s second law
Ans : c
20. Magnitude of induced emf generated in a coil is given by
(a) Fleming’s rule
(b) Lenz’s law
(c) Faraday’s first law
(d) Faraday’s second law
Ans : d
21. The frequency of DC current
(a) Equal to voltage magnitude
(b) 0
(c) Double of AC frequency
(d) 50 HZ
Ans : b
22. The current flowing in a purely inductive circuit of 30 mH on application of 230 V,
50 Hz single phase supply is 24.4 A. If the frequency of the applied voltage is
increased to 100 Hz the current flowing in the same circuit will be
(a) 24.4 A
(b) 48.8 A
(c) 12.2 A
(d) 6.1 A
Ans : c
23. Find the total resistance when two 3 Ohm resistances are connected in parallel.
(a) 1.11 ohms
(b) 1.5 ohms
(c) 0.707 ohms
(d) 1.23 ohms
Ans : b
24. Voltage drop in a resistance given by
(a) mmf/reluctance
(b) IR
(c) I/R
(d) VI
Ans : b
25. Off-line converter, SMPS has
a. AC input and dc output
b .DC input and dc output
c. AC input and ac output
d. None
Ans. a
26. Filter circuits are constructed by means of
a. Diode
b. Resistors
c. Transformers
d. Capacitor and inductors
Ans. d
27. Resistance of the diode is decreased when
a. Forward biased
b. Reverse biased
c. Both forward and reverse biased
d. Either a or b
Ans. a
28. In earlier time is used for voltage regulation.
a. Diode
b. Transistors
c. Vacuum tubes and glow bulbs
d. SMPS
Ans. c
29. is the equipment used during power failure.
a. Rectifier
b. Voltage regulators
c. UPS
d. SMPS
Ans. c
30. Peak factor of the sine wave is equal to
(a) 0.901
(b) 1.414
(c) 1.1
(d) 1.11
Ans :b
31. The amplitude of current of full wave rectified sinusoidal wave is 80 A, its average
value will be
(a) 25.44A
(b) 80A
(c) 40A
(d) 56.56A
Ans : a
32.Find the total current supplied to the lamp rated 100w .when supply voltage is 200 v.
(a) 1.75A
(b) 2A
(c) 0.5A
(d) 1A
(e) Ans : c
33. The power factor of a inductive circuit is
(a) Lagging
(b) Leading
(c) Zero lagging
(d) Unity
Ans : a
34. The power factor of a purely capacitive circuit is always
(a) Lagging
(b) Leading
(c) Unity
(d) Zero lagging
Ans : b
35. The overall circuit power factor of a RLC series circuit is found to be 0.898 lagging. The nature of the resultant circuit is
(a) Resistive
(b) Inductive
(c) Capacitive
(d) None of these
Ans : b
36. The maximum, rms and average value of a periodic current wave form is 100 A,
64.42A and 57.5A, respectively. The peak factor of this wave is
(a) 0.644
(b) 1.552
(c) 1.12
(d) None of these
Ans : b
37. In a parallel resistance circuit
(a) Power is same in all resistance
(b) Current is same in all resistance
(c) Voltage is same in all resistance
(d) Resistances are same
Ans : c
38. Find the total resistance when 2 Ohm and 4 Ohm resistances are in parallel.
(a) 1.33 Ohms
(b) 0.33 Ohms
(c) 2.33 Ohms
(d) 1 Ohm
Ans : a
39. Expression for mmf in terms of field strength is
(a) HI
(b) H/I
(c) HL
(d) H/L
Ans : c
40. is the property of magnetic which opposes the flow of flux through it.
(a) Resistance
(b) MMF
(c) Reluctance
(d) emf
Ans : c
41. is the property of electrical conductor which oppose the flow of current through it
(a) Reluctance
(b) emf
(c) mmf
(d) Resistance
Ans : d
42. Reluctance is expressed in
(a) Ampere Weber
(b) Ohm
(c) Ampere/Weber
(d) Volt/Ampere
Ans : c
43. Reciprocal of reluctance is termed as
(a) Conductance
(b) Permenance
(c) Permeability
(d) None of these
Ans : b
44. Ohm’s law for electric circuit will be
(a) emf= current/resistance
(b) emf= current X resistance
(c) emf= resistance/current
(d) emf= 1/( resistance X current)
Ans : b
45. Ohm’s law for magnetic circuit will be
(a) mmf= flux /resistance
(b) flux= mmf X resistance
(c) reluctance = mmf/ flux
(d) Resistance= mmf X flux
Ans : c
46. When the diode is ____________ biased there is current flow.
a. Forward
b. Reverse
c. Forward and Reverse
d. None of these
Ans. a
47. In half wave rectification the voltage across the load is
a. Pulsating ac
b. Pulsating dc
c. Steady
d. None of these
Ans. b
48. In half wave rectification output is
a. High
b. Very low
c. Low
d. Zero
Ans. c
49. Regulated power supply supplies
a. Constant dc voltage
b. Varying dc voltage
c. Ac voltage
d. Pulsed dc voltage
Ans. a
50. UPS is also known as
a. Switched supply
b. Battery backup
c. Both a and b
d. None of these
Ans. b
51. SMPS means
a. Switched module power supply
b. Switched mode power supply
c. supply mode power source
d. all the above
Ans. b
52. A current of 10A is flowing in series RL circuit, when it is connected across a supply
of 230 V, 50 Hz, its impedance is
(a) 23 ohm
(d) 11. 5 ohm
(c) 46 ohm
(d) 5.75 ohm
Ans : a
53. When two resistances R1,R2are connected in parallel the total resistance will be
(a) R1R2/(R1+R2)
(b) R1+R2/R1R2
(c) R1R2 X R1+R2
(d) R1+R2
Ans : a
54. Unit of inductance is
(a) Weber
(b) Ampere/Weber
(c) Henry
(d) None of these
Ans : c
55. If galvanometer deflects in opposite direction it represents ………………… in circuit.
(a) Current flow
(b) Direction of current changes
(c) Constant current flow
(d) None of these
Ans : b
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