Technical Power Electronics System Multiple Choice Questions
1. DIAC is basically
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A. A PNP/NPN transistor
B. A PNP/NPN transistor with no base connection
C. A 4 layered NPNP device
D. None of the above
Answer: B
2. The speed of an AC motor can be controlled by using
A. SCR
B. TRIAC
C. DIAC with SCR
D. DIAC with TRIAC
Answer: D
3. A power MOSFET is capable to handle current upto
A. 1 A
B. 50 A
C. 10 A
D. 100 A
Answer: D
4. An IGBT is a hybrid form of
A. A diode and a transistor
B. A transistor and SCR
C. A bipolar transistor and a MOSFET
D. A FET and a MOSFET
Answer: C
5. MOSFET’s are used in
A. Inverters
B. SMPS
C. UPS
D. All the above
Answer: D
6. High speed switching can be obtained using a
A. Power IGBT
B. PNP transistor
C. Diode
D. Vibrator
Answer: A
7. Power MOSFET and power IGBT are
A. One and the same device
B. Quite different devices
C. Similar semiconductor devices
D. Replaceable devices
Answer: C
8. Which one of the following semiconductor device may be used as a light sensor?
A. Photo diode
B. Photo transistor
C. LDR
D. Any one of the above
Answer: D
9. The material used for making optic-fibre cable in general is .
A. Copper
B. Transparent plastic
C. Aluminium
D. Steel
Answer: B
10. Which one of the following IC contains NOT gates ?
A. IC 7400
B. IC 7404
C. IC 7402
D. IC 7408
Answer: B
11. Material which can be strongly magnetised are known as materials.
A. Paramagnetic
B. Diamagnetic
C. Ferro magnetic
D. Pure magnet
Answer: C
12. What material is used for making armature core?
A. Silicon steel
B. Aluminium
C. Copper
D. Mild steel
Answer: A
13. The speed of a universal motor
A. Remains constant to the applied load
B. Is directly proportional to the applied load
C. Is inversely proportional to the applied load
D. Becomes zero when load is applied
Answer: C
14. The basic unit of inductance is
A. Farad
B. Webber
C. Henry
D. Hertz
Answer: C
15. Inductive reactance of a coil is directly proportional to the
A. Alternating current following through it
B. Induced emf in it
C. Frequency of AC flowing through it
D. All the parameters mentioned at A, B and C
Answer: D
16. Two capacitors C1 = 1 nf and C2 = 10 nf, are connected in series and applied to the battery voltage V = 11 V. What are the voltages across the capacitors?
A. VC1 = 5.5 V; VC2 = 5.5 V
B. VC1 = 10 V; VC2 = 1 V
C. VC1 = 1 V; VC2 = 10 V
D. VC1 = 0 V; VC2 = 11 V
Answer: B
17. Mutual induction is obtained by placing two current carrying coils
A. Side by side close to each other
B. Perpendicular to each other
C. Far away from each other
D. Both (1) and (2) above
Answer: A
18. The fundamental unit of measurement of resistance is
A. Ohm
B. Milli ohm
C. Kilo ohm
D. Mega ohm
Answer: A
19. For measuring unknown resistance, initially choose
A. The highest ohms range
B. The lowest ohms range
C. Any ohms range
D. R × 10 ohms range
Answer: A
20. When three resistors R1, R2 and R3 are connected in series, the total resistance `”R_T” =`
A. R1 + R2 + R3
B. R1 × R2 × R3
C. 1/R1 + 1/R2 + 1/R3
D. 1/R1 × 1/R2 × 1/R3
Answer: A
21. A charged capacitor acts like a
A. Temporary voltage source
B. Magnetic energy source
C. Constant current source
D. Switch
Answer: A
22. The relation between frequency of an AC signal (F) and time period (T) is
A. `”F=T^2″`
B. F = 2T
C. F = 1/T
D. F = 1/2T
Answer: C
23. A motor converts electrical energy into
A. Magnetic energy
B. Mechanical energy
C. Potential energy
D. Chemical energy
Answer: B
24. When 2 inductors are in parallel, the effective value of inductance is given by LT =
A. L1 + L2
B. L1 × L2/L1 + L2
C. L1 × L2
D. L1 + L2/L1 × L2
Answer: B
25. The process of adding impurities to a pure semiconductor
A. Diffusion
B. Forming
C. Etching
D. Doping
Answer: D
26. The chemical used for removing copper from copper clad boards is called
A. Thinner
B. Remover
C. Eraser
D. Etchant
Answer: D
27. In amplifiers, transistors are used for
A. Enlarging small electronic signals
B. Switching purposes
C. Reducing electronic signals
D. Both the purposes mentioned in (1) and (2)
Answer: A
28. A transistor can be thought of as two PN junction diodes connected as
A. PNPN
B. PNNP
C. NPNP
D. NNPP
Answer: B
29. The advantage of transistors over vacuum tubes is
A. Very small size
B. Minimum power loss in the form of heat
C. Low operating voltage
D. All the three, mentioned above
Answer: D
30. NPN transistors are preferred to PNP transistors for
A. Higher switching speed
B. Easy use in +ve supply rail
C. A wide range of operating temperature
D. The reasons mentioned in (1) and (2)
Answer: A
31. The number of flip-flops required to construct a decade counter is
A. 2
B. 3
C. 4
D. 6
Answer: C
32. The number of NOR gates required to construct R-S flip-flop is
A. 1
B. 2
C. 3
D. 4
Answer: B
33. The basic building block of a counter is
A. AND gate
B. OR gate
C. NAND gate
D. Flip-flops
Answer: D
34. ROM is a non-volatile memory. The name of volatile memory is
A. PROM
B. SRAM
C. EPROM
D. RAM
Answer: D
35. Modern data storage device named ‘pen drive’ has a capacity of storing 16 GB data, what does it mean
A. 16 × `”10^9″` ` `bytes
B. 16 × `”10^6″` bytes
C. 16 × `”10^9″` bits
D. 16 × `”10^6″` bits
Answer: A
36. An OP-AMP is designed to amplify
A. AC voltage
B. DC voltage
C. Both AC and DC voltage
D. Pulse signals only
Answer: C
37. DC operating voltage of IC 555 is
A. +5 to +18 V
B. +18 to +36 V
C. +5 to +28 V
D. +18 to +48 V
Answer: A
38. Approximately what is the frequency limit of the optical fibre
A. 20 GHz
B. 1 MHz
C. 100 MHz
D. 40 GHz
Answer: D
39. The higher the index number of a fibre optic cable
A. The higher the speed of light
B. The lower the speed of light
C. Has no effect on the speed of light
D. The shorter the wavelength propagation
Answer: B
40. The three major groups in the optical system are
A. The components, the data rate and response time
B. The source, the link and the receiver
C. The transmitter, the cable and the receiver
D. The source, the link and the detector
Answer: C
41. The potential difference across a PN junction is referred to as
A. Potential difference
B. Barrier potential
C. Reverse potential
D. PN potential
Answer: B
42. When a germanium diode is connected in forward biased mode the voltage across the diode will be
A. 0.7 V
B. 0.3 V
C. Is equal to applied voltage
D. 0 V
Answer: B
43. When a diode is tested using an ohm meter. It indicates the low resistance in both direction. The condition of the diode is
A. Open
B. Short
C. Leaky
D. Good
Answer: B
44. A forward biased diode starts conducting when the applied voltage reaches certain voltage known as.
A. End-in voltage
B. Barrier voltage
C. Peak voltage
D. Saturation voltage
Answer: B
45. What value of the voltage is obtained directly from the wave form shown on a C.R.O when connected across the secondary of a transformer?
A. Peak value
B. R.M.S. value
C. Peak-to-peak value
D. Average value
Answer: C
46. The main component used in a ripple filter circuit is the
A. Capacitor
B. Resistor
C. Diode
D. Transformer
Answer: A
47. The maximum forward current of an LED is about
A. 10 mA
B. 50 mA
C. .5 A
D. 1.0 A
Answer: B
48. Which colour LED has the lowest forward voltage drop?
A. Red
B. Orange
C. Green
D. Yellow
Answer: A
49. The time taken for etching PCB is in the range of
A. 5 to 20 minutes
B. 20 to 40 minutes
C. 1 to 2 hours
D. More than 2 hour
Answer: A
50. The PCB side on which components are mounted is referred to as
A. Copper side
B. Component side
C. Solder side
D. Track side
Answer: B
51. A transformer is an electrical device used to
A. change the frequency of applied AC voltage
B. transfer electrical energy from one circuit to another without any direct electrical connection
C. convert applied DC into AC
D. convert applied AC into DC
Answer: B
52. A 3-phase transformer has
A. 1 primary and 3 secondary windings
B. 3 primary and 1 secondary windings
C. 3 primary and 3 secondary windings
D. 3 primary and 6 secondary windings
Answer: C
53. A transformer has 800 turns in its primary winding and 200 in its secondary what is the primary voltage, if the secondary voltage is 40 V? Assume transformer losses as negligible?
A. 8 V
B. 16 V
C. 40 V
D. 160 V
Answer: D
54. Efficiency of a transformer is the ratio of
A. Output power to input power
B. Input power to output power
C. Input current to output current
D. Output current to input current
Answer: A
55. The basic unit of capacitance is
A. Ohm
B. Farad
C. Henry
D. Mho
Answer: B
56. The relationship between charge (Q), voltage (V) and capacitance (C) of a capacitor is
A. C = Q/V
B. C = QV
C. `”C=Q^2 V”`
D. C = V/Q
Answer: A
57. Identify the instrument which is NOT used for measurement of capacitance
A. Digital capacitance meter
B. AC bridge
C. RLC meter
D. Kelvin bridge
Answer: D
58. The capacitive reactance Xc is given by
A. 2`Pi`FC
B. 1/2`Pi`FC
C. 2`Pi`/FC
D. FC/2`Pi`
Answer: B
59. Current flowing through a capacitor is given by
A. `”V.X_c”`
B. `”V^2/X_c”`
C. `”V/X_c”`
D. `”V^2.C”`
Answer: C
60. A semi conductor in its pure form is referred to as
A. Intrinsic semiconductor
B. Extrinsic semiconductor
C. Crystal semiconductor
D. Doped semiconductor
Answer: A
61. Small signal amplifiers are also known as
A. Large power amplifiers
B. Medium power amplifiers
C. Low power amplifiers
D. Both medium power and low power amplifiers
Answer: C
62. In transistors, the width of the collector layer is
A. Much less than the base region
B. Much wider than the base region
C. Much less than the emitter region
D. Same as that of the base region
Answer: B
63. The resistance measured by a multimeter between the anode and the cathode of good SCR should be
A. Low
B. Medium
C. High
D. Infinity
Answer: D
64. In speed control circuits for DC motors using two SCR’s
A. Each SCR conducts at any time
B. One SCR conducts in positive half cycle and the other in negative half cycle
C. Both SCR’s conduct at a time
D. Only one SCR conducts and the other does not conduct
Answer: B
65. Most common application of UJT is
A. Schmitt trigger
B. Bistable multivibrator
C. Relaxation oscillator
D. Timer
Answer: C
66. Which of the following gates gives a high output with all its inputs high
A. NOT
B. NOR
C. OR
D. X-OR
Answer: C
67. The logic gate which has ‘high’ output when its inputs are different is
A. NOR
B. EX-OR
C. NAND
D. EX-NOR
Answer: B
68. The biggest advantage of ECL is
A. High fan out
B. High speed
C. Low power consumption
D. High density
Answer: B
69. The term CMOS stands for
A. Capacitance Metal Oxide Semiconductor
B. Complimentary Metal Oxide Semiconductor
C. Charged Metal Oxide Semiconductor
D. Copper Metal Oxide Semiconductor
Answer: B
70. A BCD-to-Decimal decoder converts
A. BCD code to decimal digits
B. Binary code to decimal digits
C. BCD code to binary code
D. BCD code to grey code
Answer: B
71. Silicon has an atomic number of 14, this means the atom has 14
A. Neutrons
B. Electrons
C. Protons and neutrons combined together
D. Valence electrons
Answer: B
72. The most commonly used electrical conductor is
A. Lead
B. Tin
C. Brass
D. Copper
Answer: D
73. The opposition offered to the movement of electrons/current flow is known as
A. Electric resistance
B. Current
C. Voltage
D. None of these
Answer: A
74. In a meter one main scale division is 5 volts, and it is divided into 10 small scale divisions. The meter can measure a minimum voltage of
A. 5 V
B. 0.5 V
C. 0.1 V
D. 1 V
Answer: B
75. As the field intensity (H) in the core is increased, the flux density (B)
A. Increases
B. Decreases
C. Becomes zero
D. Does not change
Answer: A
76. Magnetic lines are concentrated at
A. At the centre of magnet
B. Any one end of the magnet
C. Along the magnet uniformly
D. Both the ends of the magnet
Answer: D
77. Generation and distribution of AC power in India is normally
A. Single phase
B. 3 phase
C. 2 phase
D. Either 2 phase or 3 phase
Answer: B
78. The principle of operation of universal motor, similar to
A. DC shunt motor
B. DC series motor
C. DC short-shunt compound motor
D. DC long-shunt compound motor
Answer: B
79. The flux density of a coil can be increased by inserting a
A. Brass core
B. Iron core
C. Rubber core
D. Plastic core
Answer: B
80. The frequency of induced emf in an AC generator is given by
A. 120/PN
B. 120P/N
C. PN/120
D. 120N/P
Answer: C