Solved preview paper 3 (1to50)

Q.1. Pelton wheel is which type of turbine?
a.) Reaction turbine
b.) Impulse turbine✔
c.) Both A and B
d.) None of these

Q.2. Hey generating station has a maximum demand of 35,500 kW and has connected load of 6500 kW. The number of units generates are annually 25.6 into 10^7 the demand factor is
a.)0.646
b.)0.746
c.)0.546✔
d.)0.436

Q.3. The principle of dynamically induced EMF is utilised in:
a.) Transformer
b.) Choke
c.) Generator✔
d.)Thermocouple

Q.4. Which of the following is not a part of the dc machine
a.) Armature
b.) Commutator
c.) Field winding
d.) Damping winding✔

Q.5. 8 Ball Pool generator with 16 coils has a two layer lap winding the pole pitch is
a.)32
b.)16
c.)8✔
d.)4

Q.6. The current drawn by a 120 V DC motor with back EMF of 110 V and armature resistance of 0.04 ohms is
a.)5A
b.)25A✔
c.)275A
d.)300A

Q.7. The output indicate on the name plate of any motor is always the
a.) Gross power
b.) Power drawn in KVA
c.) Power drawn in KW
d.) Output power at the shaft✔

Q.8. When voltage in transformer from primary to secondary then it is______.
a.) Multiplied by k^2
b.) Multiplied by K✔
c.) Divided by K^2
d.) Divided by K

Q.9. A 50 Hz operation a single phase transformer has hysteresis loss 200W and Eddy current loss of 100W its core loss at 60 Hz frequency operation will be
a.)432W
b.)408W
c.)384W✔
d.)360W

Q.10. A three phase induction motor with rotor circuit open will
a.) Not run✔
b.) Run normally
c.) Get overheated
d.) Make  noise

Q.11. A 3 Phase 6 pole 50 Hz induction motor is running at 5% slip what is the speed of the motor
a.)850 rpm
b.)900 rpm
c.)950 rpm✔
d.)1000 rpm

Q.12. The starting torque of an induction motor varies as:
a.) f
b)1/f^2✔
c.)1/f
d.)f^2

Q.13. The two bright and one dark lamp method is used for
a.) Determination of phase sequence
b.) Synchronising of 3 phase alternator✔
c.) Synchronising of single phase alternator
d.) Transfer of load

Q.14. Capacitor start capacitor run motor are used in
a.) Hlists
b.) Rolling Mills✔
c.) Mining
d.) Refrigerator

Q.15. Which part of transformer is subjected to maximum heating?
a.) Frame
b.) Core
c.) Winding✔
d.) Oil

Q.16. Open circuit test in a transformer is performed with
a.) Rating Transformer voltage✔
b.) Rated Transformer current
c.) Direct current
d.) High frequency supply

Q.17. The current from the stator of an alternator is taken out to the external load circuit through
a.) Slip ring
b.) Commutator segment
c.) Solid connection✔
d.) Carbon brushes

Q.18. In rotor resistance control methods______with the increase in speed
a.) Torque increase
b.) Torque decreases✔
c.) Slip increased
d.) Losses increase

Q.19. The stator winding of a single phase induction motor is split it into two parts in order to
a.) Improve efficiency
b.) Improve power factor
c.) Develop starting torque✔
d.) Increase speed

Q.20. The cheapest system of in interval wiring is ______wiring
a.)Cleat✔
b.)Casing capping
c.)CTS or TRS
d.)Conduit

Q.21. The rating of fuse wire is always expressed in
a.)Volts
b.)Amperes✔
c.)Ampere-volt
d.) Ampere hour

Q.22. The earth potential is taken as
a.) Zero✔
b.) That of supply
c.) Infinite
d.) None of these

Q.23. Which of the following will be served as a Donor impurity in Silicon ?
a.) Boron
b.) Indium
c.) Germanium
d.) Antimony✔

Q.24. Without a DC source a clipper act like as
a.) Clamper
b.) Chopper
c.) Rectifier
d.) Demodulator✔

Q.25. For germanium P-N junction the maximum value of barrier potential is
a.) 0.3 V
b.) 0.7 V✔
c.) 1.3 V
d.) 1.7 V

Q.26. 2'S complement of the number of 1010101 is
a.) 01010 10
b.) 01010 11✔
c.) 1 10 10 10
d.) 11100 11

Q.27. An XOR  gate produces output only when two inputs are
a.) High
b.) Low
c.) Different✔
d.) Equal

Q.28. The number of flip-flop required in a decade counter
a.) 2
b.) 3
c.) 4✔
d.) 10

Q.29. A 1 mA ammeter has a resistance as 100Ω.  It is to be converted to a 1 A ammeter. The value of shunt resistance is
a.) 0.001 Ω✔
b.) 0.1001 Ω
c.) 100001 Ω
d.) 100 Ω

Q.30. The difference between the indicating value and the true value of a quantity is
a.) Gross error
b.) Absolute error✔
c.) Dynamic error
d.) Relative error

Q.31. Which one of the following metres in a integrating type instruments
a.) Ammeter
b.) Voltmeter
c.) Wattmeter
d.) Energymeter✔

Q.32. A Thermocouple Ammeter give full scale deflection at 10A .  When the ammeter read one fifth of the scale the current will be
a.) 2A
b.) 4A
c.) 4.47A✔
d.) 5.78

Q.33. Which bridge is used to determine frequency
a.) Anderson bridge
b.) De-sauty bridge
c.) Wein bridge✔
d.) Campbell bridge

Q.34. A digital voltmeter has a read out range from 0 to 9999 . When full scale reading is 9.999 V , the resolution of the full scale reading is
a.) 0.001
b) 1000
c.) 3 digit
d.) 1mV✔

Q35. In a rotating electrical machine , the insulation temperature limit for class B type is
a.)105°
b.)130°✔
c.)150°
d.)180°

Q.36. For Arc heating the electrode used are made up of :
a.) Copper
b.) Graphite✔
c.) Tungsten
d.) Aluminium

Q.37. In electric welding major personal hazards are
a.) Welding spatter
b.) Flying Sparks
c.) Harmful infrared and ultraviolet rays from arc✔
d.) All of the above

Q.38. Which of the following need the highest level of illumination
a.) Living room
b.) Kitchen✔
c.) Proof reading
d.) Hospital wards

Q.39. Long distance Railway operated on
a.) 600V dc
b.) 25 kV single phase ac✔
c.) 25 kV 3 phase ac
d.) 15 kV 3 phase ac

Q.40.The speed time curve for urban service has no
a.) Coasting time
b.) Free running period✔
c.) Breaking period
d.) Acceleration period

Q.41. Total flux required in any lighting scheme depends inversely on
a.) Surface area
b.) Illumination
c.) Coefficient of utilisation
d.) Space height ratio✔

Q.42. The least expensive drive is
a.) Belt drive✔
b.) Rope drive
c.) Chain drive
d.) Gear drive

Q.43. The ratio of the primary to secondary voltage of a transformer is 2:1 . The savings in terms of weight of copper required if an auto transformer is used instead of two winding Transformer
a.) 50%✔
b.) 33.33%
c.) 66.66%
d.) 97%

Q.44 cooling of transformer is necessary to
a.) Increase the efficiency
b.) Dissipate the heat generated in the winding✔
c.) Reduce the losses
d.) Reduce humming

Q.45. The all day efficiency of transformer is the ratio of
a.) kWh output and kWh input per day
b.) kWh output and input in a day✔
c.) Output power and input power
d.) Input power and output power

Q.46. For satisfactory parallel operation of two single phase Transformers a number  of conditions are to be fulfilled. A number of conditions are written below. Indicate which of these is not required to be fulfilled
a.) KVA rating of the two Transformers should be equal✔
b.) Transformers should be properly connected with regard to their polarity
c.) Voltage rating of the primary winding should be suitable for supply system voltage and frequency. The turn ratio of the transformer should be equal
d.) The percentage impedance of the 2 Transformer should be equal

Q.47. A 400 V 50 Hz 3 phase induction motor rotate at 1440 RPM on full load. The motor is wound for
a.) 2-poles
b.) 4-poles✔
c.) 6-poles
d.) 8-poles

Q.48. The relation between synchronous speed,  stator  supply frequency and stator number of poles of a three phase induction motor is given by
a.)Ns=P/120f
b.)f=120Ns/P
c.)f=P.Ns/120✔
d.)Ns=120P/f

Q.49. Torque developed by a three phase,  400 V induction motor is 100 N-m . If the supply voltage is reduced to 200 V that developed will be
a.) 50 N-m
b.) 25 N-m✔
c.) 200 N-m
d.) 62.5 N-m

Q.50. For a three phase induction motor having rotor circuit resistance of 6 ohm,  maximum torque occur at a slip of 0.6.  The value of stand still rotor circuit reactance is
a.) 4.44 ohm
b.) 0.36 ohm
c.) 1 ohm
d.) 10 ohm✔