2018 FEBRUARY ELECTRICIAN THEORY SEMESTER-II

2018 FEBRUARY ELECTRICIAN THEORY SEMESTER-II

1. The EMF (Es) equation of the

 transformer in the secondary side is .....
a) Eѕ= 4.44𝛟мf Nр Volt

b) Eѕ =  4.44𝛟мNѕ Volt Volt

c) Eѕ = 4.44𝛟 мf Nѕ Volt

d) Eѕ = 4.44 𝛟 мf Volt

Answer:- c) Eѕ = 4.44𝛟 мf Nѕ Volt

2. Buchholz's relay is connected in high

capacity power transformers. The purpose

of the Buchholz relay is to........

a) Arrest the flow of moisture into the tank

b) Disconnect the transformer,

    when dead short circuit fault occurs

c) Flow insulating oil from the

    conservator tank

d) Control the level of oil tank

Answer:- b) Disconnect the transformer,

    when dead short circuit fault occurs

3. A 5KVA, 400V/200V transformer

delivers a current of 25 Amps in secondary.

What is the current in primary side?

a) 50 Amps

b) 25 Amps

c) 17.5 Amps

d) 12.5 Amps

Answer:- d) 12.5 Amps

4. In full wave rectification, if the input

frequency is 50 Hz, then frequency

at the output of
filter is-

a) 50 Hz

b) 0 Hz

c) 100 Hz

d) 75 Hz

Answer:- b) 0 Hz

5. In a CE amplifier circuit the ac

    voltage between emitter and ground-

a) Is very high

b) May be high or low

c) Is zero

d) Depends upon circuit configuration

Answer:- c) Is zero

6. Which material is used for wiring

    continuous bus bar?

a) Aluminium

b) Copper

c) Both (A) and (B)

d) None of these

Answer:- a) Aluminium

7. When the coil moves at right angle to

the magnetic flux, the induced emf will be
a) Oscillating

b) Minimum

c) Zero

d) Maximum

Answer:- d) Maximum

8. Which among these is a method of wiring?

a) Joint box

b) Tee system

c) Loop in system

d) All of these

Answer:- d) All of these

9. The magnitude of the induced emf.

at zero degree angle is given by the formula

E₀ = BLVsinθ

a) Induced voltage

b) Velocity of loop rotation

c) Value of the magnetic flux density

d) Velocity of the cutting force by

magnetic lines

Answer:- b) Velocity of loop rotation

10. The direction of rotation of do

shunt motor can be reversed by

interchanging-

a) The supply terminals

b) The field terminals

c) The armature terminals only

d) Either field or armature terminals

Answer:- d) Either field or armature

                  terminals

11. With the increase in the speed

       of a do motor-

a) Both back emf as well as line current

     increase

b) Both back emf and line current fall

c) Back emf increases but the line

    current falls

d) Back emf falls and line current

     increases

Answer:- c) Back emf increases but the line

                  current falls

12. According to the IS recommendation

the clearance between the bottom part

of the ceiling
fan and the floor should not be less than -
a) 1.3 m

b) 2.0m
c) 2.25 m

d) 2.40 m

Answer:- d) 2.40 m

13. Two pin sockets should not be

used in domestic wiring unless the

appliance to be
connected is -

a) Double earthed

b) Double insulated

c) Controlled by ELCB

d) Controlled by MCB

Answer:- b) Double insulated

14. D.C. shunt motors are commonly

used in-

a) Cranes

b) Electric traction

c) Elevators

d) Lathe machines

Answer:- d) Lathe machines

15. Size of the plate electrode used for

plate earthing should not be less than -
a) 12.5x12.5x0.12 cm

b) 20 x 20 x 0.25 cm

c) 30 x 30 x 0.28 cm

d) 60 x 60 x 0.315 cm

Answer:- d) 60 x 60 x 0.315 cm

16. In which principle, the earth resistance

tester does work?

a) Fall of resistivity method

b) Fall of potential method

c) Wheatstone bridge principle       

d) Fall of conductivity method

Answer:- b) Fall of potential method

17. What is the function of current reverses

which is used in earth resistance tester?

a) To convert AC voltage into DC voltage

b) To convert DC voltage into AC voltage

c) To reduce the vibration of the pointer

d) To reduce the effect of electrolytic emf

Answer:- d) To reduce the effect of electrolytic emf

18. You have to select a PF meter

suitable for connecting in a circuit for

PF measurements on what basis you will

select its range?

a) Suitability for the type of load

     (Inductive / capacitive/ Resistance)

b) PF range of meter (Lagging /

    Leading)Unity)

c) Voltage and current range of meter

    suitable to load

d) Current and PF range of meter

     matching to load

Answer:- c) Voltage and current range of meter

    suitable to load

19. Ammeters used for current

measurements in circuits with short

over load time, differs from other

application. Ammeter used in short

overload time circuit have -
a) Non-linear scale

b) Extended scale

c) Linear scale

d) Fine scale

Answer:- b) Extended scale

20. Instruments which must not be

used in the circuit when the power is

ON are -
a) Watt meter and PF meter

b) Frequency meter and Tong tester

c) Phase sequence meter and energy

    meter  

d) Ohmmeter and Megger

Answer:- d) Ohmmeter and Megger

21. Two types of multimeters are in use.

Analog type and Digital type. Chose the

correct statement applicable for both

the types. Both the meters -

a) Have moving elements, hence must

     be used in horizontal position

b) Can be used for current and voltage

     measurement without battery

c) Need manual zero setting for

     resistance measurement

d) Need battery for resistance

    measurements

Answer:- d) Need battery for resistance

    measurements

22. Power drawn by a welding shop

which has 3 phase, 415 V, 50Hz

 supply has to be measured. The

following loads are connected,

(a) 2 welding set of each 5KVA across
L1,L2 and 13. (b) One set of 5KVA

across L2 arid L3. What is the type of

wattmeter you
would choose for this measurement?

a) 3 element 3 wire type 3 phase

    wattmeter

b) One single phase wattmeter

     connected

between any two phase and multiply

 reading by three

c) 3 element 4 wire 3 phase watt meter

d) 2 element types 3 phase watt meter

Answer:- d) 2 element types 3 phase watt meter

23. D.C shunt motor is also called as-

a) Constant flux motor

b) Constant voltage motor

c) Variable voltage motor

d) Constant current motor

Answer:- a) Constant flux motor

24. To keep the continuity of serial

 lamp set circuit even across the fuse

bulb it is customaryto connect a

device across the each bulb as precaution.

What is the name of such device?
a) NTC thermistors

b) PTC thermistors

c) Voltage dependent resistor

d) Flasher

Answer:- a) NTC thermistors

25. The starter of a fluorescent tube

 has been removed from its holder

after the tubes is lighted. What will

happen to the function of the tube?

a) Tube will begin to flicker

b) Tube will go out immediately

c) Tube will operate normally

d) Tube will begin to hum very much

 Answer:- c) Tube will operate normally

26. For a constant torque load,

if the armature resistance of

shunt motor is doubled (keeping

the shunt field constant) then the

 armature current will become-

a) Double

b) Halved

c) Remain same

d) None of these

Answer:- c) Remain same

27. Light used in the front yard

of the house should not attract

 insect in view of safety. Which
type of lamp you will avoid?

a) Mercury vapor lamp

 b) Sodium vapor lamp

c) Halogen lamp

d) GLS lamp

Answer:- a) Mercury vapor lamp

28.What is the temperature at which

a gas filled tungsten filament lamp

operates?
a) 1035° C

b)1200°
c) 1500°C

d)2300°C

Answer:- d)2300°C

29. A 4 pole, 220 V, 10 H.P, d.c.

shunt motor is rotating at a speed

of 320 rpm. The developed useful

 torque will be-

a) 210.647 N-m

b) 215.547 N-m

c) 219.484 N-m

d) None of these

Answer:- c) 219.484 N-m

30. The maximum value of sine wave

of AC voltage is 10V. What is its

RMS value?
a) 1.414 V

b) 6.060 V

c) 7.070 V

d) 14.140 V

Answer:- c) 7.070 V

31. Which of the following oscillators

 is suitable for frequencies in the range

of mega hertz?
a) RC phase shift

b) Wien bridge

c) Hartley

d) Both (a) and (c)

Answer:- c) Hartley

32. In a BJT circuit a pnp transistor is

replaced by npn transistor. To analyze

 the new circuit-

a) All calculations done earlier have

     to be repeated

b) Replace all calculated voltages

     by reverse values

c) Replace all calculated currents by

     reverse values

d) Replace all calculated voltages and

     currents by river values

Answer:- d) Replace all calculated voltages and

     currents by river values

33. When the value of capacitance is

increased in series resistance circuit,

the frequency will-
a) Decrease
b) Increase

c) No change
d) Becomes zero

Answer:- a) Decrease

34. The output indicated on the name

plate of any motor is always the-

a) Gross power

b) Power drawn in volt amperes

c) Power drawn in watts

d) Output power at the shaft

Answer:- d) Output power at the shaft

35. To protect the diodes in a rectifier

and capacitor input filter circuit it is

necessary to use-
a) Surge resistor

b) Surge inductor

c) Surge capacitor

d) Both (a) and (b)

Answer:- a) Surge resistor

36. The D.C shunt motor speed is

to be varied from zero to above

normal with reversing facility having

inherent stability of speed at all loads.

What speed control method is to be
used?

a) Supply voltage speed control

     method    

b) Ward-Leonard system of

     speed control
c) Shunt field control method

d) Armature speed control method

Answer:- b) Ward-Leonard system of

     speed control

37. An RC oscillator uses-

a) One RC combination

b) Two RC combinations

c) At last three RC combinations

d) Either (a) or (b)

Answer:- c) At last three RC combinations

38, You notice that a D.C motor starts

with jerk when starting the motor.

What may be fault for this effect?

a) line voltage too high

b) Short circuit of the field winding

c) Pitted starter contact terminals

d) Wrong grade of carbon brushes

Answer:- c) Pitted starter contact terminals

39. The gain of an FET amplifier

can be changed by changing-

a) rm

b)gm

c) Rd

d) None of these

Answer:- b)gm

40. The direction of rotation of a

D.C motor is determined by_.

a) Fleming's right hand rule

b) Fleming's left hand rule

c) Ampere's right hand grip rule

d) Maxwell's cork screw rule

Answer:- b) Fleming's left hand rule

41. A 220V, DC machine has an

armature resistance of 0.5 ohm.

If the armature current is amps,

the induced emf when the machine

work as-

(i) Generator

(ii) Motor will be respectively

a) 220V, 210V

b) 210V, 230V

c) 200V, 230V

d) 190V, 240V

Answer:- b) 210V, 230V

42. The D.C motor works on

       the principle that the-

a) Current carrying conductor

 placed in a uniform magnetic

field experiences a force on it

b) Conductor moves when kept

 in a uniform magnetic field

c) Magnetic field set up by varying

current which produces force in the

conductor

d) Combined magnetic field set up

by two current carrying conductors

produces a force between them

Answer:- a) Current carrying conductor

 placed in a uniform magnetic

field experiences a force on it

43. A DC shunt motor is running on

no-load. If the field winding gets

opened, what will be the condition

of the motor?

a) The motor will stop

b) The motor will burn out

c) The motor will run at high speed

d) The motor will make noise

Answer:- a) The motor will stop

44. The starting current of a 220V.

10 HP shunt motor having an

armature resistance of 0.2 ohms,

without starter is_.

a) 11 amps

b) 110 amps

c) 1100 amps

d) 11000 amps

Answer:- c) 1100 amps

45. The starting resistance of 3 point

starter in D.C motor is connected with_

a) Parallel across the armature

b) Series with the armature

c) Parallel across the field winding

d) Series with the field winding

Answer:- b) Series with the armature

46. The standard rated value of secondary

current of current transformer as per IS 2705
(Part 1) - 1981 shall be either_.

a) 5 Ampere or 10 Ampere

b) 2.5 Ampere or 5 Ampere

c) 1.5 Ampere or 6 Ampere

d) 1 Ampere or 5 Ampere

Answer:- d) 1 Ampere or 5 Ampere

47. The rated secondary voltage of a

 single phase potential transformer is
a) 240V

b) 230V

c) 115V

d)110V

Answer:- d)110V

48. Efficiency of transformer is

determined by knowing its input

and output power. What is the     unit

used for input and output when

calculating the all day efficiency?
a) KVAR

b) KW

c) KVA

d) KWh

Answer:- d) KWh

49. The function of conservator in a

transformer is_

a) To prevent flow of moisture into

     the tank

b) To prevent flow of air into the tank

c) To regulate the expansion and

     contraction of oil

d) To improve power factor

Answer:- c) To regulate the expansion and

     contraction of oil

50. What will happen to 415V/240V,

1KVA transformer when it is connected

to a D.C supply?

a) The output will be 240V

 b) The output will be 415V

c) The transformer may burn      .

d) Remain as it is

Answer:- c) The transformer may burn