ELECTRICAL ENGINEERING QUESTIONS AND ANSWERS FOR UPCOMING TECHNICAL EXAM.

1. In a grounded-emitter transistor, when emitter current becomes zero in cut-off region the emitter potential is called

A. Floating Emitter Potential

B. Breaking Emitter Potential

C. Cascading Emitter Potential

D. Cut-off Emitter Potential

Correct Answer : A

2. When maximum reverse-biasing voltage is applied between the collector and base terminals of the transistor and emitter is open circuited, breakdown occurs due to

A. Avalanche breakdown

B. Avalanche multiplication

C. Punch-through

D. Reach-through

Correct Answer : B

3. Which one of the following is not a distortion type that exists either separately or simultaneously in amplifiers?

A. Linear distortion

B. Non-linear distortion

C. Frequency distortion

D. Delay distortion

Correct Answer : A

4. Transistor noise caused by the recombination and generation of carriers on the surface of the crystal is called

A. Thermal noise

B. Excess noise

C. White noise

D. Shot noise

Correct Answer : D

Short noise occurs due to various reason-generation/recombination processes in bulk and depletion region, random emission of carriers across a barrier, random tunneling of carriers.

5. During a low frequency response of an amplifier which is invariably of RC-coupled type, there is a range of frequency characteristics over which the amplification is constant, and delay is also constant, called

A. Low band frequency

B. Mid band frequency

C. High band frequency

D. Hyper band frequency

Correct Answer : B

For amplifier, frequency response characteristics are divided into low, mid and high frequency. the transistor amplifier amplifies the signal faithfully in mid bond frequency only.

6. In a crystal oscillator, especially when piezoelectric crystal-like quartz is applied, then the inductor L, capacitor C and resistor R are the analogs of the mechanical system as

A. Mass, compliance,      viscous-damping factor

B. Mass, spring constant, 

viscous-damping factor

C. Mass, momentum, 

viscous-damping factor

D. Mass, displacement, viscous-damping factor

Correct Answer : A

7. In a feedback amplifier, which configuration increases bandwidth, decreases non-linear distortion and improves transconductance with negative feedback?

A. Voltage-series

B. Current-series

C. Voltage-shunt

D. Current-shunt

Correct Answer : B

8. Multivibrator circuit that remain in stable state until a triggering signal causes a transition to quasistable state and returns to stable state certain time is called

A. Astable multivibrator

B. Monostable multivibrator

C. Bistable multivibrator

D. Unstable multivibrator

Correct Answer : B

Monostable multivibrator has one stable and one quasistate. when trigger applied to it, it enters from stable to Quasi state and remains in Quasi state for a predefined time, after that time it automatically come back to stable state.

9. Which one of the following statement is not correct for an active filter used in the field of communication and signal processing?

A  It is more economical

B. It does not cause loading of the source or load

C. It is easier to tune or adjust

D. It exhibits insertion loss

Correct Answer : D

Active filter exhibits no insertion loss.

10. A graphical technique for plotting the closed-loop poles of a rational system functions as a function of the value of gain for both continuous-time and a discrete-time system is

A. Root locus method

B. Nyquist criterion method

C. Bode plot method

D. Routh-Hurwitz criterion method

Correct Answer : A

11. In time domain, the relative stability is measured by maximum overshoot and damping ratio. In frequency domain, the relative stability is measured by

A. Steady state error

B. Damping ratio

C. Resonant peak

D. Bandwidth

Correct Answer : C

12. The degree of humming level of the noise caused in the transformers may be reduced by

A. Magnetostriction

B. High flux density in core

C. Tightening of core by clamps

D. Quality of transformer oil

Correct Answer : C

The transformer humming noise is caused due to magnetostriction. A transformer is excited by an alternating current so that core is executed and contracted twice during a full cycle of magnetization. This humming noise can be reduced by tightening the core by clamps.

13. The generator efficiency of a shunt generator will be maximum when its variable loss is equal to

A. Constant loss

B. Stray loss

C. Iron loss

D. Friction and windage loss

Correct Answer : A

14. Induction motor can be regarded as a generalized transformer due to certain similarities except rated

A. Power

B. Flux

C. Speed

D. Indeed emf

Correct Answer : C

Electrical engineering Technical Awareness Questions and Answers.

Electrical engineering Technical Awareness Questions and Answers.

01. A simple method of increasing the voltag of a DC generator is

to increase the speed of rotation.

SOLUTION 
Generated voltage is directly proportional to speed. 
Generated voltage
can be increased by increasing speed of rotation.

02. For speeds higher than 3000 r. p. m.
the single phase motor used is

universal motor

SOLUTION
Full-load speeds of universal motors are from 7000 r.p.m. To 10, 000 
r.p.m.

03. The most commonly used material for insulators of overhead transmission lines

porcelain

SOLUTION
Porcelain is mechanically stronger than glass. Further, it gives less trouble from leakage and it is less affected by
temperature variations.

04. With the increase in the values of voltage and power factor, the cost of transmission line conductor

decreases.

05. following generating plants has the minimum operating cost..

hydro-electric plant.

06. The e. m. f. of a DC generator depends on

Speed.

07. Efficiency of Electrical furnaces are about

60-80% and rest heat get waste.

08. What is the maximum distance between
the two successive cleats?

0.6 m.

SOLUTION 
The distance between two successive cleats is 0. 6 m. The life period of this wiring is 3 months minimum and maximum10 to 15 years.

Cleat wiring system is a temporary wiring system therefore it is not suitable for domestic premises.

09.Which of the following devices can be used to test the windings of an inductor for continuity?

Ohmmeter.

10. Magnetic lines of force coming from a magnet

can not intersect at all.

11. The relative permeability of paramagnetic material is

greater than unity.

12. Minimum number of flip flops required to construct BCD counter is

Answer:- 4.

13. A potentiometer type instrument is used for measuring displacement, the response is

Linear.

14. The material used in high frequency
transformer core is

Ferrimagnetic.

SOLUTION
Due to high spontaneous magnetization and insulator property ferrimagnetic
material used in high frequency transformcore to reduce eddy current losses.

15. Hay's Bridge is used for

measurement of unknown inductances in terms of capacitors.

16. The most popular configuration of BJT used is

CE.

SOLUTION
As CE (Common Emitter) has highest current gain and voltage gain and
moderate input and output resistance, so it is used widely.

17. At O°k the conductivity of n type
semi-conductor is

nearly zero.

SOLUTION 
at O ° k there will be no free charge carriers available for conduction of current so,
conductivity will be nearly zero and semiconductor will act as an insulator.

18. EHT cables have rating of

33 kv to 66 kv

SOLUTION
ST cables : Super-tension cables with a rating of between 22kv to 3kv.

EHT cables : Extra high-tension cables with a rating of between 33kv and 66kv.

Extra super voltage cables : with a
maximum voltage rating beyond 132kv.

19. To measure very low resistance values the instrument used is

Kelvin's double bridge method.

20. Thyristor are used in HVDC transmission just to improve

Rating of voltage

SOLUTION
In HVDC transmission, the purpose of Thyristor is to increase the voltage rating.

Electrical Engineering RRB Technical Awareness questions and Answers.

01. As per ohm's law, what is potential
difference (V) equal to?

I.R.

SOLUTION
Ohm's law describes relationship between current and voltage in an ideal conductor

According to this law, potential difference (V) across an ideal conductor is proportional to current (I) passing through it.

Constant of proportionality is called resistance (R)
So, V=l.R.

02. Reaction between which of the followingtwo reactants will produce hydrogen gas?

Magnesium and
hydrochloric acid.

03. Which gas burns with popping sound?

Hydrogen

SOLUTION
· Hydrogen is a combustible gas
· Hydrogen gas is highly flammable that forms explosive mixtures with air
· The pop sound is due to small explosionformed by burning of hydrogen with
oxygen.

04. How can the sensitivity of a
potentiometer be increased?

By increasing the length
Of wire. 

SOLUTION 
The sensitivity of a potentiometer can be increased by increasing the length of the potentiometer wire and by reducing the current in the circuit by using a rheostat.

05. Plants are biotic as they are living beings.

Heat, Light and temperature are all abiotic factors as they are not living.

06. An object will continue to accelerate until

Resultant force on it is zero.

SOLUTION
An object continues to accelerate until itis stopped by an external force.

As per Newton's second law of motion,

F=ma

a = F/m

So, as per this law, when resultant forceon an object is zero,
Acceleration is zero.

07. When a magnetic needle is kept
in a non-uniform magnetic field, it
experiences?

A force and torque.

08. What is the use of CO2. Lasers in an
Industry?

Cutting and welding.

09. The water convert to water vapour at

100°C or 373 Kelvin.

10. The primary color in VDU (Visual Display Unit)

are RGB (Red, Green, Blue).

A VDU displays images generated by a computer or other electronic device.

11.  following communication modes support two-ways traffic but in only one direction at a time

Half-duplex.

12. In series LCR circuit, at resonance

current is maximum, power factor is unity.

13. The series magnet of a single phase Energy meter consists of coil of

thick wire of few turns.

14. The dummy coil in DC machines is used to

bring about mechanical balance of armature.

15. In an R-C-L series circuit, during
resonance, the impedance will be

minimum.

16. In interconnected grid system, more
efficient plants are used as

base load stations

SOLUTION
A base load station supplies almost a
constant load through out the day I. e. For24 hours. Therefore, more efficient plants are used as base load stations.

17. To supply peak load of a power station,

diesel power plants is very suitable.

SOLUTION
Peak load power stations deliver power for brief intervals in a day. Such stations must be put in service very quickly.

Consequently, they are equipped with
prime movers such as diesel engines and gas turbines that can be started up in a
few minutes. 

18. The voltage regulation of a d.c. generatoris zero. This implies that generator is

Flat compounded.

19. Which of following instruments has the highest torque/weight ratio among the given instruments?

Permanent magnet moving coil instrument.

20. What is the maximum number of lighting points that can be connected in a circuit?

Answer:- 10.

SOLUTION

At least 1 circuit for lighting. Each circuitsupplying a maximum of 10 lighting
points.

21. There are mainly three types of insulatorare used as overhead insulator like wise

Pin Insulator,
Suspension Insulator,
Strain Insulator.

22. In an alternator that  is the most dangerous fault and are likely to cause considerable damage to the expensive machinery

That is The stator winding faults.

23. A low lagging power factor results in

poor voltage regulation.

24. The demand factor on a power station is

always lesser than unity

SOLUTION
Demand factor = maximum demand /
Connected load

The demand factor is always lesser than unity because the maximum demand is always less than the connected load.

25. When the length of transmission line increases, the resistance (R) of the line

increases.

Induction Machine top mcq.

01.The frequency of the induced emf in an induction motor is

Same as the supply frequency.

02.In an induction motor, the air gap flux density is usually kept low so as to

improve power factor


03.The frame of an induction motor is usually made of

Cast iron.

04.A wound rotor motor is mainly used in applications where 

speed control is required.

05.When the supply frequency of a three phase induction motor is increased, then its synchronous speed is

 increases.

06.In a double squirrel cage induction motor, the outer cage winding has 

high resistance.

07.In induction motor, greater the number of poles

 Lesser the speed.

08.The no-load speed of an induction motor depends upon

the number of its poles.

09.The operation of an induction motor is based on

Lenz's law.

10.At no load induction motor has possible power factor as

0.2.

11.A capacitor start single phase induction motor will usually have a power factor of

0.6 lagging.

12.Which part will surely tell that given motor is DC motor and not an AC type?

Commutator 

Commutator.

Explanation:- Commutator is used only in DC machine for providing mechanical rectification.

13.A resistance split-phase induction motor is used for

high inertia loads.

14.A capacitor-start, capacitor -run motor has

high power factor.

15.The washing machine generally employs 

resistance split-phase motors.

16.universal motor and hysteresis motor is an a.c. motors and 

universal motor 

synchronous type.

17.A reluctance motor runs at

synchronous speed.

18.In ac series motor the purpose of providing compensating winding is to

reduce sparking at brushes.

19.A d.c. series motor is accidentally connected to single phase supply. The torque produced will be

pulsating and unidirectional.

20.repulsion motor has the 

largest starting torque.

Power system top mcq part 2

01.Which distribution system is more reliable?

Ring main system.

02.The insulation resistance test is performed on power line with

meggar.

03.The power output from an hydroelectric power plant depends on

discharge, head and system efficiency.

04.In hydroelectric power plants

Operating cost is low and initial cost is high.

05.The flow duration curve at a given head of a hydroelectric plant is used to determine

total power available at the site.

06.In high head hydroelectric power plant, the velocity of water flow in penstock is around

7 m/s.

07.The function of a surge tank is to

relieve water hammer pressures in the penstock pipe.

08.The maximum head of a Kaplan turbine is limited to

25 m.

09.The pumped storage scheme is employed to supply

during the peak hours.

10.High tension cables can be used for transmission of voltage upto

66 kv.

11.With the increase in transmission voltage, the volume of the conductor will

decrease.

12.Alternator are rated in

KVA.

13.A thermal plant has an efficiency of about

30%.

14.High voltage transmission is recommended because it

Reduces the cross-section area of the conductor.

15.The permissible variation in supply frequency is

+ 5%.

16.Series reactors are used to :

bring down the fault level within the capacity of the switchgear.

17.SF6 gas is transported in

liquid form in cylinders.

18.Plug setting of an electromagnetic relay can be altered by varying

number of ampere turns.

19.The most efficient torque– producing actuating structure for induction-type relays is

induction-cup structure.

20.Buchholz relay to

connected in the pipe connecting main tank of transformer and conservator.

21.The Buchholz protects a transformer from

types of internal faults.

Power system top mcq part 1

01.A relay used on short transmission lines is

Reactance relay.

02.The main advantage of AC transmission system over DC transmission system is

less losses in transmission over long distances.

03.For the transmission of same power

AC line requires more copper than a DC line.

04.If the length of a cable is double , its capacitance

becomes double.

05.HT cables are generally used upto

11 kV.

06.In a transmission line insulators are used

suspension type.

07.Porcelain insulators are glazed because

to prevent absorption of gases and water vapour.

08.The function of circuit breaker is

to safe guard the circuit.

09.The type of insulator used for holding the HT overhead ocnductor on straight running of poles ?

Pin-type insulators.

10.A 11 kV underground cable is layed at a depth of

0.9 m.

11.Rewirable fuse is also known as

kit-kat fuse.

12.The fusing factor of HRC fuse is

1.1

13.Time delay relay is used in which relay type

thermal relay.

14.Single bare copper wire having voltage of

230 V.

15.The symmetrical components are used in the fault analysis because

the sequence networks do not have mutual couplings.

16.In a star-connected system without neutral grounding, zero-sequence currents are

zero.

17.A balanced 3-phase system consists of

positive-sequence currents only.

18.The positive sequence current of a transmission line is :

equal to negative current.

19.Negative-sequence reactance of a transformer is

equal to the positive-sequence reactance.

20.The material used in liquid fuses is

carbon tetra chloride.

21.HRC fuses have the advantage(s) of

high speed operation,

high rupturing capacity,

no ageing effect,

all of the above.

22.In HRC fuse the time between cut-off and final current zero is called the

arcing time.

23.For a circuit breaker 'break time' is

opening time + arc duration + resistor current duration.

24.When a fault occurs in a high voltage transmission line, first the

relay operates, then successively the isolator and the circuit breaker.

Control system mcq

Control system mcq.

01.The transform function of a system is the Laplace transform of

impulse response.

02.The transfer function is defined as
  
linear time in variant systems.

03.What is the characteristic of a good control system ?

Insensitive to parameter variation but sensitive to input commands.

04.The transfer function of a linear system is the

ratio of the Laplace transform of the output and that of the input with all initial conditions zeros.

05.Despite the presence of negative feedback, control system still have problems of instability because the

components used have non linearities.

06.In a control system, the use of negative feedback

reduces the effects of disturbance and noise signals in the forward path.

07.When a human being tries to approach an object, his brain acts as?​

An error measuring device.

Basic electronics most imp mcq.

01.The emitter of a transistor is generally doped the heaviest because it

has to supply the charge carriers.

02.Voltage power supplies use a high resistance across the output of the supply. That resistance is called

bleeder resistors.

03.For a NPN bipolar transistor, diffusion of holes is the 

main stream of current in the base region.

04.Application of DC voltage to a diode, transistor, or other device to produce a desired mode of operation is called

biasing.

05.The transistor configuration which provides highest output impedance is 

Common Base.

06.For transistor, turn-off time that is

Sum of storage time and fall time.

07.The emitter resistor RE is bypassed by a capacitor in order to

increase the voltage gain.

08.The action of a JFET in its equivalent circuit can best be represented as a

Voltage Controlled Current Source.

09.An electron in the conduction band

Has a higher energy than an electron in the valence band.

10.Resistivity of a semiconductor depends upon–
  
Atomic nature of the semiconductor.

11.In an intrinsic semiconductor

Both electrons and holes carry current.

12.In a good conductor, the energy gap between the conduction band and the valence band is 

Zero.

13.The energy band gap of silicon is

1.1 eV.

14.P-type semiconductor is prepared by doping silicon or germanium semoconductor by

Trivalent impurity atoms.

15.N-type semiconductor is obtained when silicon or germanium is doped 

Phosphorus.

16.P-type semiconductors are–

Electrically neutral.

17.The addition of a very small quantity of aluminium to a silicon or germanium crystal makes it

P-type semiconductor.

18.The most commonly used semiconductor is

Silicon.

19.An intrinsic semiconductor at the absolute zero of temperature

Behaves like an insulator.

20.The forbidden energy gap is largest in the case of 

Insulators.

21.The majority carriers of electricity in a N-type semiconductor are

Free electons.

22.The addition of pentavalent impurity to a semiconductor creates more

Free electrons.

23.Reverse bias on a junction diode

Raises the junction potential barrier.

24.The width of the depletion layer in a P-N junction diode

Increases when a reverse bias is applied.

25.Nucleus is made of

Protons and neutrons.