15-05-2017, 04:57 PM
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203/2014
Maximum : 100 marks
Time : 1 hour and 15 minutes
1.Cells are connected in parallel in order to :
(A)increase the voltage available
(B)reduce cost of wiring
(C )increase the current available
(D)reduce the time required to fully charge them after use
2.The combined resistance of two equal resistors connected in parallel is equal to :
(A)one half the resistance of one resistor
(B)twice the resistance of one resistor
(C )four times the resistance of one resistor
(D)one fourth the resistance of one resistor
3.Superposition theorem can be applicable only to circuits having------------elements.
(A)non-linear
(B)passive
(C ) resistive
(D)linear bilateral
4.The speed of an induction motor :
(A)decreases too much with the increase of load
(B)increases with the increase of load
(C )decreases slightly with the increase of load
(D)remains constant with the increase of load
5.Which DC motors has approximately constant speed?
(A)Series motor
(B)Shunt motor
(C )Cumulatively compound motor
(D)All of the above
6.Under t he condition of resonance, RLC scries circuit behaves as a :
(A)purely resistive circuit
(B) purely inductive circuit
(C ) capacitive circuit
(D) reactive Circuit
7.A UJT contain? :
(A)four pn junction?
(B)three pn junctions
(C ) two pn junction?
(D) one pn junction
8.The ripple factor of a power supply is a measure of:
(A)its voltage regulation
(B) its diode rating
(C ) purity of power output
(D) its filter efficiency
9.The synchronous speed for a 3 phase 6-pole induction motor is 1200 rpm. If the number of poles is now reduced to 4 with the frequency remaining constant, the rotor speed with a slip of 5% will be :
(A)1690 rpm
(B) 1750 rpm
(C ) 1500 rpm
(D) 1710 rpm
10.A device whose characteristics are very close to that of an ideal voltage source is :
(A) a vaccum diode
(B) a DLAC
(C ) a zener diode
(D) a PET
11.When converting 7,000 nA to microamperes, the result is :
(A) 0.007 ft A
(B) 0.7 //A
(C ) 700 uA
(D) 7 uA
12.The ‘sheath’ is used in cable to :
(A)provide strength to the cable
(B)provide proper insulation
(C )prevent the moisture from entering the cable
(D)avoid chances of rust on strands
13.When the speed at which a conductor is moved through a magnetic Held is increased, the induced voltage?
(A) increases
(B) decreases
(C ) remains constant
(D) reaches zero
14.The induced voltage across a coil with 250 turns that is located in a magnetic field that is changing at a rate of 8 Wb/s is :
(A)1,000 V
(B) 2.000 V
(C )31.25 V
(D)3,125 V
15.Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will ho the frequency of the rotor induced emt?
(A)10 Hz
(B)50 Hz
(C )1 Hz
(D)2500 Hz
16.The eddy current loss in an a-c electric motor is 100 watts at 50 Hz. Its loss at 100 Hz will be :
(A)25 watts
(B)59 watts
(C )100 watts
(D)400 watts
17.The armature of a dc machine is laminated to reduce :
(A)Eddy current loss
(B)Hysteresis loss
(C )Copper losses
(D)Friction and windage losses
18.A single phase Hysteresis motor :
(A)can run at. synchronous speed only
(B)can run at sub synchronous speed only
(C )can run at synchronous and super synchronous speed
(D) run at synchronous and sub synchronous speed
19.The temperature of resistance furnaces can he controlled by changing the :
(A) applied voltage
(B) number of heating elements
(C )circuit configuration
(D)all of the above
20.For a line voltage V and regulation of a transmission line R :
(A)RkV
(B)VR?1
(C )2R∞.V
(D)2VR ∞ 1
21.The rotor frequency for a 3 phase 1000 RPM 6 pole induction motor with a slip of 0.04 is — -----------Hz.
(A)8
(B)4
(C )6
(D)2
22.When two transformers are operating in parallel, they will share the load as under?
(A)proportional to their impedances
(B)inversely proportional to their impedances
(C )50% - 50%
(D)25% - 75%
23.A 3 - phage, 400 volts, 50Hz, 100 KW, 4 polo squirrel cage induction motor with a rated slip of 2% will have a rotor speed of:’.
(A)1500 rpm
(C )1530 rpm
(B)1170 rpm
(D)1570 rpm
24.A 3 — phase, 400 volts, 50 Hz. 100 KW, 1 pole squirrel cage induction motor with a rated slip of 2% will have a rotor speed of:
(A)1500 rpm
(C )1530 rpm
(B)1470 rpm
(D)1570 rpm
25.The voltage al the two ends of a transmission line are 132 KV and its reactance is 40 ohm. The Capacity of the line is :
(A)435.0 MW
(B) 217.8 MW
(C )251.5 MW‘
(D)500 MW
26.A-synchronous motor is operating on no-load at unity power factor. Tf the field current is increased, power factor will become :
(A)lagging and current will decrease
(B)lagging and current will increase
(C )leading and current will decrease
(D) leading and current will increase
27.A d.c. shunt motor runs at no loadspeedof1110 r.p.m. At full load,armaturereaction weakensthe main flux by 5% whereas the armature circuit voltage dropsby10%. The motor full load speed in r.p.m. is :
(A)1200
(B)1203
(C )1000
(D)1080
28.The most suitable servomotor for low power applications is :
(A) a dc series motor
(B) a dc shunt motor
(C )an ac two-phase inductionmotor
(D) an ac series motor
29.A 400 kw, 3-phase, 440 V, 50 Hz induction motor has a speed of 950 r.p.m. on full load. The machine has 6 poles. The slip of the machine will he :
(A)0.06
(B) 0.10
(C )0.04
(D)0.05
30.In a salient pole synchronous machine (usual symbols are used):
(A)xq > xd
(B)xq - xd
(C )xq < xd
(D)xq = 0'
31.CRGO laminations in a transformer are used to minimise :
(A)eddy current loss
(B)hysteresis loss
(C )both (A) and (B)
(D)ohmic loss
32.An Air-core transformer, as compared to iron core transformer, has :
(A)less magnetic core loss
(B)more magnetic core loss
(C )no magnetic core loss
(D)less ohmic loss
33.Transformer maximum efficiency, for a constant load current, occurs at:
(A)0.8 pf
(B)zero pf leading
(C )zero pf lagging
(D)unity power factor
34.A dc series motor is running .at rated speed with rated excitation. The motor has two resistance and R2 connected across the animture and the field respectively. Speeds above the rated speed can he achieved by :
(A)decreasing R1 only
(B)increasing R2 only
(C )decreasing and increasing R1
(D)increasing R1 and decreasing R2
35.A dc series motor is running at rated speed without any additional resistance in series. If an additional resistance is placed in series, the speed of the motor :
(A)increases
(B)decreases
(C )remains unchanged
(D)oscillates around the rated speed
36.Plugging of dc motors is normally executed by :
(A)reversing the field polarity
(B)reversing the armature polarity
(C )reversing both armature and field polarity
(D)connecting a resistance across the armature
37.The direction of induced emf in an armature coil of a dc machine is :
(A)the same as that of the current for both the generator and the motor
(B)opposite to that of the current for the generator and the motor
(C )the same as that of current for the generator and opposite to that of the current for the motor
(D)none of these.
38.The wave form of the armature mmf in a dc machine is :
(A)square
(B)rectangular
(C )triangular
(D)sinusoidal
39.Mass of a proton is how many times greater than mass of an electron :
(A)184000
(B)18100
(0)1840
(D)184
40.Conductance of any conductor is expressed as :
(A)ampere/watt
(B)mho
(C )volt/watt
(D)watt/ampere-
41.Two resistances R1 and R2 give combined resistances 4.5 Ω and 1 Ω when they are connected in series and parallel respectively. What would be the values of these resistances?
(A)3 Ω and 6Ω
(B) 6ft and 90
(C )30 and 90
(D)1.5 Ω and 3Ω
42. Kirchhoffs second law is based on law of conservation of:
(A) charge
(B)energy
(C ) momentum
(D)mass
43.Ampere second is the unit of:
(A) conductance
(B)power
(C ) energy
(D)charge.
43.An electric current of 6 A is same as :
(A) 6 joule/second
(B)6 coulomb/second
(C ) 6 watt/second
(D)none of the above
45.The colour band sequence of a resistor is Yellow, Violet, Orange and Mold. The range in which its value must Lie so as to satisfy the tolerance specified is between :
(A)44.66 KW and 49.35 KW
(B)44.65 KW and 49.35 KW
(C )44.65KW and49.36 KW
(D)45 KW and 49.34KW
46.The Secondary line voltage is maximum for which of the following connections :
(A)Della — Delta
(B)Star - Star
(C )Delta - Star
(D)Star — Delta
47.The crawling in an Induction Motor is caused by :
(A) Improper Design of Machine
(B)Low voltage supply
(C ) High Loads
(D)Harmonics Developed in the motor
48.Speed variations of a squirrel cage Induction motor are essentially similar to those of :
(A) DC Shunt motor
(B) DC Series motor
(C ) Synchronous motor
(D) Differential compound
49.The no-load ratio of a 50 Hz single phase transformer is 6000/250 V .The maximum flux in the core is 0.06 wb. What is the number of primary’ turns?
(A)450
(B)900
(C ) 350
(D) 210
50.A 23/2300 V transformer takes no load current of 5 A at 0.25 power factor lagging. The core loss is:
(A) 300.2 W
(B)192.5 W
(C ). 287.5 W
(D)212.6 W
51. The power taken by a 3-phase load is given by the expression :
(A) 3Vl1l cos
(B)√3 VL IL cos
(C ) √3VLlL sin
(D)3VL 1L sin
A semiconductor is formed bybonds. .
(A) Covalent
(B)Electrovalent
(C ) Co-Ordinate
(D)None of the above
53.After firing an SCR, the gating pulse is removed. The current in the SCR will:
(A)Remains the same
(B)Immediately fall to zero
(C )Rise up
(D)Rise a little and then fall to zero
54.The majority carriers in a semiconductor are produced by :
(A)Bound Electrons
(B)Electron - Hole pairs
(C )Doping
(D)None of the above
55.The leakage current in a crystal diode is due to :
(A)Junction Capacitance
(B)Majority Carriers
(C )Minority and Majority Carriers
(D)Minority Carriers
56.A series resistance is connected in the zener circuit to :
(A)properly reverse bias the zener
(B)protect the zener
(C )properly forward bias the zener
(D)current amplifier
57.Stray losses in an induction motor generally are :
(A)proportional to the square of the stator current
(B)proportional to the square of the rotor current
(C )proportional to the rotor current
(D) inversely proportional to the square of rotor current
58.What determines the thermal loading on the motor?
(A)Duty/Load cycle
(B)Temperature of the winding
(C )Age of the motor
(D)Ambient conditions
59.The speed of an AC motor depends on :
(A)Frequency
(B)No. of poles
(C )Both (A) and (B)
(D)None of the above
60.Reduction in supply voltage by 10% will change the torque of the motor by (A)38%*
(B)19%
(C )9.5%
(D) no change
61.Output power requirements of constant torque loads vary with :
(A) speed
(B) voltage
(C ) current
(D) power factor
62.A crystal diode is a------------—- device.
(A) non-linear
(B)linear
(C ) amplifying
(D) none of the above
63.A pn junction acts as a :
(A) unidirectional switch
(B) bidirectional switch
(C ) controlled switch
(D)none of the above
64.The rotor power output of a 3-phase, induction The rotor copper loss will be motor is 15 KW and corresponding slip is 4% :
(A) 600 W
(B) 625 W
(C )650 W
(D)700 W
65.The busbar protection means protection of:
(A) Busbar
(B) Isolating switches
(C ) Circuit breakers
(D)All.above
66. A circuit breaker is able to open under
(A) no load conditions
(B) load conditions
(C )fault conditions
(D) none of above
67. Reactors are connected
with the system.
(A) in series
(B)in parallel
(C ) in series parallel
(D)none of above
68.The distribution transformer is rated in :
(A) KW
(B)KVAR
(C ) KVA
(D)none of above
69.Voltaic of primary distribution system is :
(A) 400 V
(B)33 KV
(C ) 230 V
(D)11 KV
70.If the span is increased, the sap:
(A) decreases
(B)increases
(C ) remains same
(D)none of above
71.In India, the transmission of electric power is done by:
(A) 3-phase, 3-wire system
(B)3-phase, 4-win
(C ) 1-phase system
(D)none of above
72.Decimal 15 in binary system can be written as :
(A) 1000
(B)1110
(C ) 1100
(D)1111
73.In cascading which of the following configurations is normally used?
(A) CC
(B)CB
(C ) CE
(D)All of the above
74.The input impedance of a transistor under forward bias is :
(A) high .
(B)low
(C ) very high
(D)almost zero
75.Motor preferred for blowers is :
(A) wound rotor induction motor
(B)D.C shunt motor
(C ) .squirrel cage induction molars
(D)D.C series motor
76.Slip rings are usually made of:
(A) carbon or graphite
(B)brass or steel
(C ) silver or gold
(D)copper or aluminium
77.The colour code of a resistor of nominal value 2.7K Ω10 % is :
(A) Red, violet, red and silver
(B)Red, violet, yellow and gold
(C ) Red. violet, orange and silver
(D)Red, violet, red and gold
78.A reluctance motor:
(A) is self starting
(B)is constant speed
(C ) needs on D.C. excitation
(D)all of the above
79.A Power transformer is a constant:
(A) voltage device
(B)current device
(C ) power device
(D)main flux device
80.Permeance is the reciprocal of:
(A) flux density
(B)reluctance
(C ) ampere-turns
(D)resistance
81.The form factor of a sinusoidal wave is :
(A) 1.414
(B)2
(C ) 1.11
(D)1.5
82.Which of the following is a ferromagnetic material?•
(A) Tungsten
(B)Aluminium
(C ) Copper
(D)Nickel
83.An oscillator converts :•
(A) a.c. power into d.c. power
(B)d.c. power into a.c. power
(C ) mechanical power into a.c power
(D))none of above
84.The frequency of DC supply is :
(A) Zero
(B) 1Hz
(C )50 Hz
D)100 Hz
85. Relative permeability of vacuum is :
(A)4/r
(B)1 H/m
(C ) 1
(D)1/4
86.The basic unit of electric charge is :
(A)ampere-hour
(B)watt-hour
(C )coulomb
(D)farad
87.Semiconductor material have------------Bonds.
(A)ionic
(B)covalent
(C )mutual
(D)metallic
88. The binary system uses power of for positional values.
(A) 2
(B)10
(C ) 8
(D) 16
89. An active element is :
(A) Resistance
(B) Inductor
(C ) Current source
(D) All of above
90. A d.c. motor is used to :
(A)generate power
(B)change mechanical energy to electrical energy
(C )change electrical energy to mechanical energy
(D) increase energy put into it
91.instruments are mostsensitive.
(A)moving-iron
(B)hot-wire
(C )dynamometer
(D)permanent-magnet moving coil
92. The most commonly used cell is :
(A)lead-acid cell
(B)nickel-iron cell
(C )nickel-cadmium cell
(D)fuel coll
93. The efficiency of a primary'cell is about:
(A)25%
(B)15%
(C )70%
(D) 35%
94.Inductance opposesin current in a circuit.
(A) only increase
(B) only decrease
(C ) change
(D) steady
95. When a magnet is heated
(A)it gains magnetism
(B)it loses magnetism
(C )it neither loses or gam magnetism
(D)it gains capacitance
96. Iron is ferromagnetic :
(A) above 770°C
(B) below 770°C
(C ) at all temperature
(D) none of above
97. For the process of electrolysis, we require :
(A) d.c. supply
(B) a.c. supply
(C ) varying voltage
(D) both d.c and a.c supply
98. The average value of sin 0 over a complete cycle is:
(A) zero
(B) +1
(C ) -1
(D) 1/2
99. As compared to shunt and compound DC motors, the series DC motor will have the highest torque because of its comparatively-----------------at the start.
(A) Lower armature resistance
(B) Stronger series field
(C ) Fewer series turns
(D) Larger armature
100. Moving-iron instruments havescale.
(A)squared
(B)uniform
(C )log
(D)none of above