Electrical Engineering Quiz 5

1 / 50

Materials subjected to rapid reversal of magnetism should have______________?

high co-ercivity and high retentivity

high co-ercivity and low density

large area oiB-H loop

high permeability and low hysteresis loss

2 / 50

The maximum efficiency of resistance loaded class A power amplifier is _________________?

50%

25%

30%

3 / 50

In split-phase motor auxiliary winding is of___________?

thin wire placed at the top of the slots

thick wire placed at the top of the slots

thin wire placed at the bottom of the slots

thick wire placed at the bottom of the slots

4 / 50

Long distance railways use which of the following ?

25 kV three phase A.C.

25 kV two phase A.C.

25 kV single phase A.C.

200 V D.C.

5 / 50

What will be the magnetic potential difference across the air gap of 2 cm length in magnetic field of 200 AT/m ?

4 AT

6 AT

2 AT

10 AT

6 / 50

Insertion of reactance in the rotor circuit_______?

increases starting torque as well as maximum torque

reduces starting torque as well as maximum torque

increases starting torque but maxi-mum torque decreases

increases starting torque but maxi-mum torque remains unchanged

7 / 50

If the load resistance decreases in a Zener regulator, then Zener current ______________?

Increases

Stays the same

None of the above

Decreases

8 / 50

The curve between V and I of SCR when anode is positive w.r.t cathode and when anode is negative w.r.t cathode are known as_____________________?

former as reverse characteristics and later as forward characteristics

former as forward characteristics and later as reverse characteristics

both as reverse characteristics

both as forward characteristics

9 / 50

Relative permeability of vacuum is__________?

4n x 10-? H/m

1/4JI

1 H/m

10 / 50

The power scale of circle diagram of an induction motor can be found from__________?

noue of the above

short-circuit test only

stator resistance test

no-load test only

11 / 50

In a series parallel circuit, any two resistances in the same current path must be in___________?

series with the voltage source

parallel with each other

series with each other

parallel with the voltage source

12 / 50

During discharge, the active material of both the positive and negative plates is changed to___________?

Pb02

PbO

PbS04

13 / 50

Parson?s turbine is___________?

simple single wheel, impulse steam turbine

pressure compounded steam turbine

simple single wheel reaction steam turbine

multi wheel reaction steam turbine

14 / 50

What is used to protect a thyristor from high di / dt conditions__________?

Fuse.

Snubber circuit

Inductor

Voltage clamping device

15 / 50

The Q of the crystal is of the order of____________?

More than 10,000

1000

100

16 / 50

Short-circuit test on an induction motor cannot be used to determine___________?

power scale of circle diagram

transformation ratio

copper losses

windage losses

17 / 50

The best indication about the state of charge on a lead-acid battery is given by____________?

specific gravity of electrolyte

output voltage

temperature of electrolyte

none of the above

18 / 50

Copper brushes in D.C. machine are used_____________?

where high voltage and small cur-rents are involved

in none of the above cases

in both of the above cases

where low voltage and high currents are involved

19 / 50

In a rotary converter I2R losses as compared to a D.C. generator of the same size will be___________?

double

same

three times

less

20 / 50

capacitors are used for audio frequency and radio frequency coupling and tuning ?

Mica

Air

Ceramic

Plastic film

21 / 50

Which of the following alternatives will be cheaper ?

Five motors of 20 H.P. each

Four motors of 25 H.P. each

A 100 H.P. A three phase motor

Ten motors of 10 H.P. each

22 / 50

PVC stands for____________?

pressed and varnished cloth

polyvinyl chloride

post varnish conductor

positive voltage conductor

23 / 50

The following constitute short-circuit in the armature winding.

Insulation failure between two commutator bars

Insulation failure between two turns of a coil

Two of more turns of the same coil getting grounded

All of the above

24 / 50

All of the following are equivalent to watt except_____________?

amperes/volt

(amperes) ohm

amperes x volts

joules/seC.

25 / 50

In conductors conduction of electricity takes place due to movement of_______________?

positive ions only

positive and negative ions

negative ions only

electrons only

26 / 50

Volt box is a component to_____________?

extend voltage range

compare voltage in a box

none of the above

measure voltage

27 / 50

The attraction capacity of electromagnet will increase if the_______________?

flux density decreases

core area increases

flux density increases

core length increases i

28 / 50

In resistance heating highest working temperature is obtained from heating elements made of_____________?

nichrome

silver

silicon carbide

nickel copper

29 / 50

Which of the following motor has the poorest speed regulation ?

Series motor

Differential compound motor

Shunt motor

Cumulative compound motor

30 / 50

The effects of EMI can be reduced by_____________?

Reducing the efficiency of the coupling path

Reducing the susceptibility of the receptor

All of these

Suppressing emissions

31 / 50

When a conductor carries more current on the surface as compared to core, it is due to___________?

permeability variation

skin effect

unsymmetrical fault

corona

32 / 50

In a series resonant band-pass filter, a lower value of Q results in______________?

a higher resonant frequency

a higher impedance

a smaller bandwidth

a larger bandwidth

33 / 50

An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is____________?

2 Wb

0.02 Wb

20 Wb

0.2 Wb

34 / 50

The leakage current across a pn junction is due to________________?

None of the above

Majority carriers

Junction capacitance

Minority carriers

35 / 50

A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 K The voltage and current rating of available SCRs are 1800 V and 1000 For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be_____________?

6, 4

4, 6

7, 5

5, 7

36 / 50

If the anode current is 800 A, then the amount of current required to turn off the GTO is about____________?

600 A

200 A

400 A

20 A

37 / 50

When an ammeter is inserted in the circuit, the circuit current will _____________?

None of the above

Decrease

Increase

Remain the same

38 / 50

In parallel resonance, the circuit impedance is_________________?

C/LR

CR/L

R/LC

L/CR

39 / 50

Six resistors are in parallel. The two lowest-value resistors are both 1.2 k?. The total resistance______________?

is less than 1.2 k?

is less than 6 k?

is greater than 1.2 k?

is less than 600 ?

40 / 50

What will be the collector efficiency of a power amplifier having zero signal power dissipation of 5 watts and a.c. power output of 2 watts ?

20%

40%

50%

80%

41 / 50

IC = aIE +____________?

ICBO

?IB

ICEO

42 / 50

Mercury is a choice with steam in binary vapour cycle because it has____________?

relatively low vapourisation pressure

all above

higher critical temperature and pressure

higher saturation temperature than other fluids

43 / 50

Damping of the Ballistic galvanometer is made small to_______________?

get first deflection large

get minimum overshoot

make the system oscillatory

make the system critically damped

44 / 50

If a 6 uF capacitor is charged to 200 V, the charge in coulombs will be____________?

800 uC

1600 uC

1200 uC

900 uC

45 / 50

Total number of crystal systems is____________?

46 / 50

During load shedding:

system frequency is reduced Efficiency is the secondary consideration in

system power factor is changed

system voltage is reduced

some loads are switched off

47 / 50

For Parson?s reaction steam turbine, degree of reaction is____________?

50%

75%

100%

60%

48 / 50

1 volt/meter is same as___________?

1 newton meter

1 meter/coulomb

1 newton/meter

1 joule/coulomb

49 / 50

To send 10% of the main current through a moving coil galvanometer of resistance 99 O the shunt required is______________?

100 O

9 O

11 O

50 / 50

In a shaded pole single-phase motor, the revolving field is produced by the use of_________?

shading coils

capacitor

inductor

resistor

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