ELECTRICIAN THEORY

SEMESTER-II

PART-1

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