Electrical Engineering Quiz 48

1 / 50

The power factor of a single-phase induction motor is usually?

lagging

unity

unity to 0.8 leading

always leading

2 / 50

If two sine waves of the same frequency have a phase difference of JT radians, then_______?

when one wave reaches its maxi?mum value, the other will reach its minimum value

none of the above

both will reach their maximum values at the same instant

both will reach their minimum values at the same instant

3 / 50

The minimum dielectric stress in a cable is at_____________?

armour

bedding

conductor surface

lead sheath

4 / 50

It is advisable to avoid line-starting of induction motor and use starter because__________?

it will pick-up very high speed and may go out of step

it will run in reverse direction

motor takes five to seven times its full load current

starting torque is very high

5 / 50

Transformer coupling is used for__________amplification?

Current

Power

Voltage

None of the above

6 / 50

Sulphated cells are indicated by____________?

the decrease of the specific gravity

all above conditions

the low voltage of the cell on discharge

the loss of capacity of the cell

7 / 50

A rotory converter can also be run as a___________?

d.c. series motor

synchronous motor

d.c. compound motor

d.c. shunt motor

8 / 50

Armature reaction in a generator results in_____________?

magnetising the center of all poles

damagnetising the center of all poles

demagnetisation of leading pole tip and magnetisation of trailing pole tip

demagnetisation of trailing pole tip and magnetisation of leading pole tip

9 / 50

A transformer can have zero voltage regulation at______________?

leading power factor

lagging power factor

zero power factor

unity power factor

10 / 50

Which method can be used for absolute measurement of resistances _______________?

Ohm?s law method

Releigh method

Wheatstone bridge method

Lorentz method

11 / 50

In a capacitor the electric charge is stored in____________?

both (A) and (B)

metal plates

dielectric

none of the above

12 / 50

Which of the following is unit of inductance ?

Webers/metre

Ohm

Ampere turns

Henry

13 / 50

Induction cup relay is operated due to changes in________________?

current

all of the above

impedance

voltage

14 / 50

For commutation in three phase PAC, normally balanced three phase voltages VR, VY and VB are connected to the three legs of the converter via______________?

Three capacitances

Three transistors

Three inductances

Three resistance

15 / 50

Conductance is reciprocal of____________?

inductance

resistance

reluctance

capacitance

16 / 50

An npn BJT has gm=38mA/v, c? =10?14 F, c? =10?13F and DC current gain ?0=90.For this transistor fT & f? are________?

fT =1.47 x 1010 Hz & f? = 1.33 x 1012 Hz

fT =1.47 x 1010 Hz & f? = 1.64 x 108 Hz

fT =1.64 x 108 Hz & f? = 1.47 x 1010 Hz.

fT =1.33 x 1012 Hz & f? = 1.47 x 1010 Hz

17 / 50

The purpose of a coupling capacitor in a transistor amplifier is to ___________________?

Increase the output impedance of transistor

Provide biasing

Pass a.c. and block d.c.

Protect the transistor

18 / 50

The purpose of stator winding in the compensated repulsion motor is to_____________?

provide mechanical balance

prevent hunting in the motor

improve power factor and provide better speed regulation

eliminate armature reaction

19 / 50

In case of conductively compensated D.C. series motors, the compensating winding is provided______________?

in series with armature winding

in parallel with field winding

as separately wound unit

in parallel with armature winding

20 / 50

A field line and an equipotential surface are____________?

always at 90?

inclined at any angle 0

none of the above

always parallel

21 / 50

Life of the batteries is in the following ascending order____________?

Edison cell, Nickel-cadmium cell, lead-acid cell

Lead-acid cell, Nickel-cadmium cell, Edison cell

Lead-acid cell, Edison cell, Nickel cadmium cell

Nickel-cadmium cell, Edison cell, lead-acid cell

22 / 50

When a rectangular voltage waveform is applied to a capacitor, then the current waveform is ______________?

Square

Rectangular

Sawtooth

Sinusoidal

23 / 50

The efficiency of an electrolytic rectifier is nearly____________?

40%

60%

80%

70%

24 / 50

In the circle diagram for induction motor, the diameter of the circle represents____________?

slip

line voltage

rotor current

running torque

25 / 50

For forced draught system, the function of chimney is mainly_____________?

to discharge gases high up in the atmosphere to avoid hazard

to produce draught to accelerate the combustion of fuel

none of the above

to reduce the temperature of the hot gases discharged

26 / 50

Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

High core losses

Low short circuit ratio

Low field current

High field current

27 / 50

Paramagnetic materials have relative permeability________________?

slightly more than unity

equal to unity

equal to that ferromagnetic mate rials

slightly less than unity

28 / 50

The diameter of the rotor shaft for an electric motor depends on which of the following ?

Horse power, r.p.m. and power factor

r.p.m. only

Horse power and r.p.m.

Horse power only

29 / 50

Which of following is normally ON device?

SIT

TRIAC

BJT

IGBT

30 / 50

Transformer coupling is generally employed when load resistance is______________?

Large

Very large

None of the above

Small

31 / 50

. If =0.98 ,Ico=6?A and I?=100?A for a transistor,then the value of Ic will be______?

3.2mA

2.3mA

5.2mA

4.6 mA

32 / 50

A Weston synchronoscope is a________________?

none of the above

dynamometer instrument

moving coil instrument

moving iron instrument

33 / 50

At a certain frequency, the output voltage of a filter is 6 V and the input is 12 V.the filter?s bandwidth is____________?

11.5 Hz

530 Hz

106 Hz

53 Hz

34 / 50

The reverse recovery time of diode is trr = 3 Î¼s and the rate off all of the diode current is di/dt = 30 A/Î¼s. The storage charge current QRR is___________?

130 Î¼s

135 Î¼s

140 Î¼s

145 Î¼s

35 / 50

The value of E within the field due to a point charge can be found with the help of___________?

Coulomb?s laws

Kirchhoff s laws

Faraday?s laws

none of the above

36 / 50

Interruption of large currents by relay requires______________?

wide separation of the opened contacts

all of the above

high speed opening of contacts

arc suppressing blow out coils

37 / 50

Method which is commonly applied for unloading the coal for small power plant is___________?

tower cranes

belt conveyor

lift trucks

coal accelerators

38 / 50

The bandwidth of a single stage amplifier is_____________that of a multistage amplifier?

Less than

More than

Data insufficient

The same as

39 / 50

When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of_____________?

either of the above

full pitch

none of the above

short pitch

40 / 50

__________ will be least affected due to charge in supply voltage frequency.

Mixer grinder

Electric clock

Room heater

Ceiling fan

41 / 50

In an induction motor if air-gap is increased__________?

bearing friction will reduce

windage losses will be more

copper loss will reduce In an induction motor

the power factor will be low

42 / 50

The metallic spheres A and B of radii 2m and 4m respectively carry the same charge 4 x 10 8 If the spheres are connected by a copper wire_______________?

charge will flow from A to B

charge will flow from B to A

both a and b are possible

no flow of charge will occur

43 / 50

In case of impulse steam turbine_____________?

there is enthalpy drop in fixed and moving blades

there is enthalpy drop only in moving blades

there is enthalpy drop in nozzles

none of the above

44 / 50

For the transmission of heat from one body to another__________?

both bodies must be in contact

temperature of the two bodies must be different

both bodies must be solids

at least one of the bodies must have some source of heating

45 / 50

Ferrites are materials

ferromagnetic

none of the above

paramagnetic

diamagnetic

46 / 50

__________________can be extended to systems which are time-varying ?

State model representatives

Root locus design

Transfer functions

Bode-Nyquist stability methods

47 / 50

Conductivity is analogous to____________?

inductance

resistivity

permeability

retentivity

48 / 50

In a simple magnetic field the strength of magnet flux_______________?

decreases continuously from initial value to final value

is constant and has same value in energy part of the magnetic field

first increases and then decreases till it becomes zero

increases continuously from initial value to final value

49 / 50

If d.c. supply of 10 V is fed to a differentiating circuit, then output will be_______________?

10 V

0 V

20 V

None of the above

50 / 50

In a certain low-pass filter, fc = 3.5 kHz.if the input voltage is a 6 V sine wave with a dc level of 10 V, what is the output voltage magnitude?

5.97 V

6 V

0 V

597 mV

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