Electrical Engineering Quiz 31

1 / 50

The time constant of the capacitance circuit is defined as the time during which voltage________?

falls to 36.8% of its final steady value

rises to 38.6% of its final steady value

rises to 63.2% of its final steady value

none of the above

2 / 50

Copper, even though costly, finds use in the windings of electrical machines because_____________?

copper points offer low contact resistance

copper can be easily soldered and welded

None

all of the above

3 / 50

Dry cell is modification of____________?

Leclanche cell

Edison cell

Lead-acid cell

Deniell cell

4 / 50

If the power level of an amplifier reduces to half, the db gain will fall by___________?

3 db

2 db

5 db

10 db

5 / 50

As load on an induction motor goes on increasing______________?

its power factor goes on increasing up to full load and then it falls again

its power factor goes on decreasing

its power factor goes on increasing even after full load

its power factor remains constant

6 / 50

In a regenerative feed heating cycle, the greatest economy is affected___________?

when steam is extracted from several places in different stages of steam turbine

when steam is extracted only from the last stage of steam turbine

when steam is extracted from only one suitable point of steam turbine

when steam is extracted only from the first stage of steam turbine

7 / 50

Annual depreciation of the plant it proportional to the earning capacity of the plant vide

none of the above

sinking fund depreciation

reducing balances depreciation

straight line depreciation

8 / 50

An SCR has three terminals viz ________________?

Cathode, anode, gate

Anode, cathode, grid

None of the above

Anode, cathode, drain

9 / 50

In an induction motor the relationship between stator slots and rotor slots is that_____________?

none of the above

stator slots are not exact multiple of rotor slots

stator slots are equal to rotor slots

stator slots are exact multiple of rotor slots

10 / 50

Depreciation charges are high in case of__________?

diesel plant

thermal plant

hydroelectric plant

none of these

11 / 50

Mutually inductance between two magnetically-coupled coils depends on____________?

permeability of the core

the number of their turns

cross-sectional area of their common core

all of the above

12 / 50

No-load current in a transformer________________?

lags behind the voltage by about 75?

leads the voltage by about 15?

leads the voltage by about 75?

lags behind the voltage by about 15?

13 / 50

Magnetism of a magnet can be destroyed by_____________?

hammering

heating

by inductive action of another magnet

by all above methods

14 / 50

Which of the following devices is used for conversion of co-ordinates ?

Selsyn

Synchro-resolver

Microsyn

Synchro-transformer

15 / 50

When current feedback (negative) is applied to an amplifier, its input impedance _____________?

Remains the same

Is decreased

Is increased

None of the above

16 / 50

The value of emitter capacitor CE in a multistage amplifier is about____________?

50 ?F

0.01 ?F

100 pF

1 ?F

17 / 50

In a resistance furnace the atmosphere is_____________?

oxidizing

reducing

neutral

deoxidising

18 / 50

An induction motor is__________?

non-self starting

self-starting with high torque

self-starting with zero torque

self-starting with low torque

19 / 50

Shunt generators are most suited for stable parallel operation because of their______________?

linear voltage characteristics

identical voltage characteristics

drooping voltage characteristics

rising voltage characteristics

20 / 50

The output power of the cascaded amplifier / attenuator system can be determined using___________?

Actual gain of attenuator

Actual gain of amplifier

Actual gain of amplifier and attenuator

Gain in dB of amplifier and attenuator

21 / 50

In a JFET, IDSS is known as ________________?

drain to source current with gate open

drain to source current with gate shorted

drain to source current

none of the above

22 / 50

Digital ICs process______________?

Digital signals only

None of the above

Both digital and linear signals

Linear signals only

23 / 50

Following D.C. generator will be in a position to build up without any residual magnetism in the poles______________?

shunt generator

self-excited generator

series generator

compound generator

24 / 50

In coal preparation plant, magnetic separators are used to remove___________?

clinkers

dust

sand

iron particles

25 / 50

In forward blocking mode of a thyristor________?

junction J2 is in reverse bias and J1, J3 is in forward bias.

Junction J1, J3 is in reverse bias and J2 is in forward bias.

junction J3 is in forward bias and J1, J2 is in reverse bias.

Junction J1 and J2 is in forward bias and J3 is in reverse bias.

26 / 50

In constant voltage charging method, the charging current from discharged to fully charged condition_____________?

none of the above

increases

remains constant

decreases

27 / 50

The electric charge of 100 ?C is 13cm apart from another charge 16.9?C electric force between them is_____________?

900N

9x106N

9x105N

9x107N

28 / 50

Mains a.c. power is converrted into d.c. power for_________________?

using in electronic equipment

none of the above

lighting purposes

heaters

29 / 50

Due to which of the following reasons the cables should not be operated too hot ?

The oil may loose its viscosity and it may start drawing off from higher levels

Expansion of the oil may cause the sheath to burst

Unequal expansion may create voids in the insulation which will lead to ionization

All of the above

30 / 50

A signal other than the reference input that tends to affect the value of controlled variable is known as_________________?

reference input

control element

command

disturbance

31 / 50

Voltage commutation circuit can be converted into a current commutation by interchanging the positions of____________?

Capacitor and SCR

Capacitor and load

Inductor and capacitor

Diode and capacitor

32 / 50

In _________ system fuel from a central pulverizing unit is delivered to a bunker and then to the various burners?

All

unit

central

none of the above

33 / 50

The capacitance between two plates increases with____________?

larger plate area, longer distance between plates and higher,applied voltage

larger plate area and shorter distance between plates

shorter plate area and shorter distance between them

shorter plate area and higher applied voltage

34 / 50

The change of cross-sectional area of conductor in magnetic field will affect______________?

resistance of conductor

reluctance of conductor

none of the above

All

35 / 50

Low power factor is usually not due to___________?

arc lamps

incandescent lamp

fluorescent tubes

induction motors

36 / 50

The rapid wear of brushes takes place due to____________?

rough commutator bars

excessive spring pressure

abrasion from dust

all of the above factors

37 / 50

A sinusoidal voltage with a peak-to-peak value of 18 V is applied to an RC low-pass filter. If the reactance at the input frequency is zero, the output voltage is____________?

18 V peak-to-peak

9 V peak-to-peak

12.74 V peak-to-peak

zero

38 / 50

In an induction motor, no-load the slip is generally____________?

less than 1%

1.50%

39 / 50

Suri transmission is_________________?

mechanical-electrical

hydro-pneumatic

electrical-pneumatic

hydro-mechanical

40 / 50

The latching current of GTO should be of order

1:00 AM

500 mA

100 mA

2:00 AM

41 / 50

H.R. fuses provide best protection against________________?

overload

open-circuits

short-circuits

reverse current

42 / 50

In the squirrel-cage induction motor the rotor slots are usually given slight skew__________?

none of the above

to ensure easy fabrication

to increase the tensile strength of the rotor bars

to reduce the magnetic hum and locking tendency of the rotor

43 / 50

Steel wire is used as____________?

earth wire

core wire of ACSR

overhead telephone wire

all of the above

44 / 50

Silicon steel used in lamination?s mainly reduces___________?

hysteresis loss

all of the above

copper losses

eddy current losses

45 / 50

In arc furnace the function of choke is______________?

to reduce severity of the surge

to imprpve, power factor

none of the above

to stabilize the arc

46 / 50

The advantage of oil filled cables is_________?

smaller overall size

more perfect impregnation

no ionisation, oxidation and formation of voids

all of the above

47 / 50

Introducing a resistor in the emitter of a common amplifier stabilizes the dc operating point against variations in____________?

only the ? of the transistor

None of the above

Both Temperature & ?

Only the temperature

48 / 50

A voltage divider consists of two 68 k? resistors and a 24 V source. The unknown output voltage is______________?

24 V

0 V

12 V

6 V

49 / 50

A centrifugal switch is used to dis- connect ?starting winding when motor has___________?

run for about 5 minutes

picked up about 10 to 25 per cent of rated speed

run for about 1 minute

picked up about 50 to 70 per cent of rated speed

50 / 50

Reheat factor is the ratio of_____________?

cumulative actual enthalpy drop for the stages to total is isentropic enthalpy heat drop

isentropic heat drop to useful heat drop

adiabatic heat drop to isentropic heat drop

None

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