NLC GET Electrical Fuzzy Systems MCQ Part 1

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NLC GET Electrical Fuzzy Systems MCQ Part 1

1.Fuzzy logic is a form of
A. Two-valued logic
B. Crisp set logic
C. Many-valued logic
D. Binary set logic
Answer-C

2.The room temperature is hot. Here the hot (use of linguistic variable is used. can be represented by
_______ .

A. Fuzzy Set
B. Crisp Set
C. Both of these
D. None of these
Answer-A

3.Fuzzy Set theory defines fuzzy operators. Choose the fuzzy operators from the following
A. AND
B. OR
C. NOT
D. All of these
Answer- D

4.Fuzzy logic is usually represented as
A. IF-THEN-ELSE rules
B. IF-THEN rules
C. Both a & b
D. None of the mentioned
Answer- B
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5.______________ is/are the way/s to represent uncertainty.
A. Fuzzy Logic
B. Probability
C. Entropy
D. All of these
Answer-D

6.____________ are algorithms that learn from their more complex environments (hence eco) to generalize, approximate and simplify solution logic.
A. Fuzzy Relational DB
B. Ecorithms
C. Fuzzy Set
D. None of these
Answer-C

7.What is the form of Fuzzy logic
A. Two-valued logic
B. Crisp set logic
C. Many-valued logic
D. Binary set logic
Answer-C

8.The truth values of traditional set theory is ____________ and that of fuzzy set is __________
A. Either 0 or 1, between 0 & 1
B. Between 0 & 1, either 0 or 1
C. Between 0 & 1, between 0 & 1
D. Either 0 or 1, either 0 or 1
Answer-A

9.The values of the set membership is represented by ___________
A. Discrete Set
B. Degree of truth
C. Probabilities
D. Both Degree of truth & Probabilities
Answer-B

10.There are also other operators, more linguistic in nature, called __________ that can be applied to fuzzy set theory.
A. Hedges
B. Lingual Variable
C. Fuzz Variable
D. None of the mentioned
Answer-A

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11.Traditional set theory is also known as Crisp Set theory.
A.TRUE
B. FALSE
C. Traditional set theory is not there.
D. None of the Above
Answer-A

12.Which of the following is not Application Areas of Fuzzy Logic
A.Automotive Systems
B. Domestic Goods
C. Domestic Control
D. Environment Control
Answer-C

13.The values of the set membership is represented by ___________
A. Discrete Set
B. Degree of truth
C. Probabilities
D. Both Degree of truth & Probabilities
Answer-D

14.Who was the inventor of Fuzzy Logic
A. Doug cutting
B. John McCarthy
C. Lotfi Zadeh
D. John cutting
Answer-C

15.How many output Fuzzy Logic produce
A.2
B. 3
C. 4
D. 5
Answer-A

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16.How many main parts are there in Fuzzy Logic Systems Architecture
A.3
B. 4
C. 5
D. 6
Answer-B

17.Which of the following is not a part of fuzzy logic Systems Architecture
A.Fuzzification Module
B. Knowledge Base
C. Defuzzification Module
D. Interference base
Answer-D

18.Fuzzy logic is useful for both commercial and practical purposes
A.True, False
B. True, True
C. False, False
D. False, True
Answer-B

19.What is Fuzzy Logic
A. a method of reasoning that resembles human reasoning
B. a method of question that resembles human answer
C. a method of giving answer that resembles human answer.
D. None of the Above
Answer-A

20.Fuzzy Logic can be implemented in
A.Hardware
B. software
C. Both A and B
D. None of the Above
Answer-C
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TYPES OF STAIRS

 TYPES OF STAIRS
.
➡️Depending upon the various arrangement of steps, stairs can be classified under following categories:
.
1. STRAIGHT STAIR:
In this stair, all the steps are arranged continuously
along in one direction. One flight may be split into
one or more than one flight by interposing a
landing. This stair can be used where narrow and
long space is available for a staircase such as
entrance, porch etc.
.
2. DOGGED-LEGGED STAIR: This stair consists of two straight flights of steps with direct turns between them. This stair is very useful where the total width of the stair is just twice the width of the steps.
.
3. OPEN NEWEL STAIR:
This type of stair consists of two or more flights
arranging a well or opening between the backward
and forward flights. When all the steps are difficult
to arrange in two flights, a short third flight of 3 to
6 steps may be provided along the direction
perpendicular to the hall. Open newel stair is mostly
adopted in the lift.
.
4. GEOMETRICAL STAIR:
This is another type of open newel stair where the
open well between the forward and the backward
flight is curved. This stair may contain different
geometrical shape. Here the change in direction is
achieved by using winders.
.
5. CIRCULAR STAIR:
In this type of stair, all the steps radiate from a newel or well hole, in the form of winders.
The circular stair is adopted at the back side of a building to access its various floors.
6. SPIRAL STAIR:
Spiral stair is very similar to a circular stair. It consists of individual steps or treads, connecting to a centre column. The overall diameter of the stair may range from 1 to 2.5 m.
.
7. QUARTER-TURN STAIR:
The quarter-turn stair can be defined as the stairs
that are turned at 90 degrees with the help of level landing.
.
8. BIFURCATED STAIR:
This type of stair is provided in modern public
buildings as well as residential buildings. In this stair, the flight is so arranged that there is a wide flight at the start which is sub-divided into narrow flights at the mid-landing. The narrow flights start from either side of the mid landin

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DIFFERENT TYPES OF DEFECTS FOUND ON BRICKS

 DIFFERENT TYPES OF DEFECTS FOUND ON BRICKS.

1. BLOATING
This defect observed as spongy swollen mass over the surface of burned bricks. This is caused due to the presence of excess carbonaceous matter and sulphur in brick-clay.

2. CHUFFS
The deformation of the shape of bricks caused by the rain water falling on hot bricks is known as chuffs.

3. SPOTS
Iron sulphide, if present in the brick clay, results in dark surface spots on the brick surfaces. Such bricks though not harmful are unsuitable for exposed masonry work.

4. BLISTERS
Broken blisters are generally caused on the surface of sewer pipes and drain tiles due to air imprisoned during their moulding.

5. LAMINATIONS
These are caused by the entrapped air in the voids of clay. Laminations produce thin lamina on the brick faces which weather out on exposure

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Definitions of terms Of Masonry

 Definitions of terms Of Masonry
.

1. Course : A course is a horizontal layer of bricks stones 

2. Bed : the surface of a stone perpendicular to the line of pressure of (lower surface of bricks or stones in each course)

3. Back : The inner surface of wall not exposed is called back. 
The material forming back is known as backing 

4. Face : The exterior of the wall exposed to weather is known 
as face. The material used in the facing of wall is known as 
facing

5. Hearting : It is the interior portion of a wall between facing 
and backing 

6. Head : It is a brick or stone, which lies with its greatest length  at right angles to the face of the work. 

7. Stretcher : It is a brick or a stone which lies with its congest 
side parallel to the face of the work 

8. Bond : The method of arranging bricks so that the individual  units are tied together
 
9. Spalls : The chips of stones used for filling the interstices in 
stone masonry
 
10. Quoins : The stones used for the corners of walls of structure 

11. Bat : It is a portion of a brick cut across the width. 

12. Closer: It is the portion of a brickcut in such a manner that its  one long face remains uncut 

13. Queen closer: it is the portion of a brick obtained by cutting a  brick length-wise into two portions

14. King closer: It is the portion of brick obtained by cutting off 
the triangular piece between the centre of one end and the 
centre of one side. 

15. Bevelled closer: It is the portion of a brick in which the 
whole length of the brick is bevelled for maintaining half 
width at one end and full width at the other 

16. Frog : It is an indentation or depression on the top face of a 
brick made with the object of forming a key for the mortar. 

17. Sill : It is a horizontal stone, concrete or wood, employed for 
the purpose of shedding off rain water from the face of wall 
immediately below the window opening 

18. Corbel : It is the extension of one or more course of stone or 
brick from the face of a wall to serve as a support for wall 
plates

19. Templates : Pieces of stones placed under the end of a beam 
to distribute load over a greater area. 

20. Coping : It is the course placed upon the exposed top of an  external wall to prevent the seepage of water 

21. Buttress : It is a sloping or stepped masonry projection from a  tall wall intended to strengthen the wall against the thrust of a roof
.
#BuildingConstruction
#Masonary
.

1. Course : A course is a horizontal layer of bricks stones

2. Bed : the surface of a stone perpendicular to the line of pressure of (lower surface of bricks or stones in each course)

3. Back : The inner surface of wall not exposed is called back.
The material forming back is known as backing

4. Face : The exterior of the wall exposed to weather is known
as face. The material used in the facing of wall is known as
facing

5. Hearting : It is the interior portion of a wall between facing
and backing

6. Head : It is a brick or stone, which lies with its greatest length  at right angles to the face of the work.

7. Stretcher : It is a brick or a stone which lies with its congest
side parallel to the face of the work

8. Bond : The method of arranging bricks so that the individual  units are tied together
 
9. Spalls : The chips of stones used for filling the interstices in
stone masonry
 
10. Quoins : The stones used for the corners of walls of structure

11. Bat : It is a portion of a brick cut across the width.

12. Closer: It is the portion of a brickcut in such a manner that its  one long face remains uncut

13. Queen closer: it is the portion of a brick obtained by cutting a  brick length-wise into two portions

14. King closer: It is the portion of brick obtained by cutting off
the triangular piece between the centre of one end and the
centre of one side.

15. Bevelled closer: It is the portion of a brick in which the
whole length of the brick is bevelled for maintaining half
width at one end and full width at the other

16. Frog : It is an indentation or depression on the top face of a
brick made with the object of forming a key for the mortar.

17. Sill : It is a horizontal stone, concrete or wood, employed for
the purpose of shedding off rain water from the face of wall
immediately below the window opening

18. Corbel : It is the extension of one or more course of stone or
brick from the face of a wall to serve as a support for wall
plates

19. Templates : Pieces of stones placed under the end of a beam
to distribute load over a greater area.

20. Coping : It is the course placed upon the exposed top of an  external wall to prevent the seepage of water

21. Buttress : It is a sloping or stepped masonry projection from a  tall wall intended to strengthen the wall against the thrust of a roof
.
#BuildingConstruction
#Masonary


Stone masonry ( part two )

👉 The construction of stones bonded together with  mortar is termed as stone masonry

🔸 Different types of stones 
used for different purposes

1. Heavy engineering works : Granite, gneiss 

2. Buildings situated in industrial towns :- Granite and compact  sandstone

3. Pavements, railway ballast, doorsits and  steps  :- Granite slabs and  slate

4. Electrical switch board :- Marble slabs and  slate

5. Fire resistance works :- Compact sandstone 

6. Carving and ornamental works :-  Marble and laterite 

7. Face work and architectural purposes :- Marble, granite closer  gained sand stone
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Design Of Columns As Per ACI and Concrete Cover Distance for Reinforcement Bar

Design Of Columns As Per ACI

1- Maximum and Minimum Reinforcement Ratio
The minimum reinforcement ratio of 1 % is to be used in tied or spirally reinforced columns. This minimum reinforcement is needed to safeguard against any bending, reduce the effect of shrinkage and creep and enhance the ductility of columns.

2- Minimum Number of Reinforcing Bars
Minimum four bars within rectangular or circular sections; or one bar in each corner of the cross-section for other shapes and a minimum of six bars in spirally reinforced columns should be used.

3- Clear Distance between Reinforcing Bars
For tied or spirally reinforced columns, clear distance between bars should not be less than the larger of 150 times bar diameter or 4 cm.

4- Concrete Protection Cover
The clear concrete cover should not be less than 4 cm for columns not exposed to weather or in contact with the ground. It is essential for protecting the reinforcement from corrosion or fire hazards.

5- Minimum Cross-Sectional Dimensions
For practical considerations, column dimensions can be taken as multiples of 5 cm.

6- Lateral Reinforcement

Ties are effective in restraining the longitudinal bars from buckling out through the surface of the column, holding the reinforcement cage together during the construction process, confining the concrete core and when columns are subjected to horizontal forces, they serve as shear reinforcement. Spirals, on the other hand, serve in addition to these benefits in compensating for the strength loss due to spalling of the outside concrete shell at ultimate column strength
7- Ties
For longitudinal bars, 32 mm or smaller, lateral ties 10 mm in diameter should be used. In some countries, ties of 8 mm dia are used for column construction. .



👉Concrete Cover Distance for Reinforcement Bar



▶️The reinforcement must be fixed with appropriate accuracy in the position specified by the designer to ensure proper structural performance, durability and fire resistance. *Insufficient cover can result in corrosion of the reinforcement, leading to cracking and spalling of the concrete and eventually, if left unchecked, to a reduction in the cross-sectional area of the reinforcement and in the strength of the structure. The cover must also be sufficient to provide the required degree of fire resistance. Too little cover reduces the fire resistance; too much, unless precautionary measures are taken, can make the structure vulnerable to spalling, which again reduces the fi re resistance. Incorrect positioning of the reinforcement can seriously reduce the load-carrying capacity of the structural member.
*Unless otherwise specified, the concrete cover to the reinforcement should be within the following permissible deviations from the dimensions specified in BS 8110:
:
*Bars up to 12 mm diameter: +5mm –5mm
*Bars over 12 mm up to 25 mm: +10 mm –5mm
*Bars over 25 mm: +15 mm –5mm
:
▶️At each end of reinforcing bar, net less that 25 mm or less than twice the diameter of the bar.
*For a longitudinal reinforcing bar in a column, not less than 40 mm not less than the diameter of such bar.
*In case of columns of minimum dimension of 20 cm or under, whose reinforcing bards do no not exceed 12 mm a cover of 25 mm to be used.
*For longitudinal reinforcing bars in a beam, not less than 30 mm or less than the diameter of the bar.
*For tensile, compressive shear or other reinforcements in a slab or wall not less than 15 mm, not less that the diameter of such bar.
*For any other reinforcement not less than 15 mm, not less than the diameter of such bar.
*For footings and other principal structural members in which the concrete is deposited directly against the ground, cover to the bottom reinforcement shall be 75 mm. If concrete is poured on a layer of lean concrete, the bottom cover maybe reduced to 50 mm.
*For concrete surfaces exposed to the weather or the ground after removal of forms, such as retaining walls, grade beams, footing sides and top etc. not less than 50 mm.
*Increased cover thickness shall be provided as indicated on the drawings, for surfaces exposed to the action of harmful chemicals (or exposed to earth contaminated by such chemicals), acid, alkali, saline atmosphere, sulphorone, smoke etc.
*For liquid retaining structures, the minimum cover to all steel shall be 40 mm or the diameter of the main bar, whichever is greater. In the presence of sea water and oils and waters of a corrosive character the covers, shall be increased by 10 mm.
Protection to reinforcement in case of concrete exposed to harmful surroundings may also be given by providing a dense impermeable concrete with approved protective coatings. In such a case the extra cover mentioned in (b) & (i) above may be reduced.
:
▶️The correct cover shall be maintained by cement mortar cubes (blocks) or other approved means. Reinforcements for footings, grade beams and slabs on a sub-grade shall be supported on re-cast concrete blocks as approved by EIC.
*The use of pebbles or stones shall not be permitted.



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100 MCQ OF Synchronous Generator or Alternator with Explanation Part-10

PKR TECH CLASSES

100 MCQ OF Synchronous Generator or Alternator with Explanation

91.The disadvantage of a short-pitched coil is that...............

Harmonics are introduced

Voltage around the coil is Increased

Waveform becomes non-sinusoidal

Voltage around the coil is reduced

In the case of full pitch winding the pole pitch and coil span are equal to 180 degrees.



As we can see in the figure one coil cut N pole and other coil cut S pole which results in the phase difference of 180 degrees.

The full pitch winding offer full induced emf but it causes harmonic distortion.

Talking about Short pitch winding the pole pitch is slightly less than to pole pitch by an angle α.



For reducing 3rd harmonic from generated emf

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Cos(3α/2) = 0

3α/2 = π/2 α = π/3 = 60°

Therefore the value of α should be 60 degrees.

Some advantages of short-pitch winding are

Due to the shortening span, the copper required is less.
Low copper losses
Improve waveform due to the reduction in harmonic
Fractional Pitch winding reduces sparking in DC machines

Disadvantages of Short Pitch Coil:

Since in a fractional pitch winding, the two sides of a given coil are not at the corresponding points under the adjacent poles.Hence the e.m.f. induced in the two sides is slightly out of phase and the coil e.m.f. is less than if the full pitch was used with the same number of turns. In order to compensate for this reduction in Generated EMF, more the number of turns and therefore more copper is required.

92.The per-phase D.C armature resistance of an alternator is 0.5 ohm. The effective AC armature resistance would be about?

1 ohm

0.25 ohms

0.75 ohms

0.5 ohms

Since there are harmonics generated in individual coils of the alternator windings, some high frequencies are present. Due to skin effect, the effective a.c resistance of armature winding is greater than its d.c. resistance. The factor of difference varies according to the base frequency and winding arrangement and is from 1.2 to 1.8. It is the usual practice to take a.c. armature resistance as 1.5 times the d.c. resistance for 50 Hz machine.

Rac = 1.5 Rdc = 1.5 x 0.5

Rac = 0.75Ω

93.The d.c. armature resistance of a Y connected alternator measured across its two terminals is 0.5 Ω. The per-phase resistance is

10.5 Ω

1.5 Ω

0.25 Ω

1 Ω

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Consider the star connection. Every armature winding has its own resistance. The effective resistance of an armature winding per phase is denoted as Ra Ω/ph.

Generally, the armature resistance is measured by applying the known d.c. voltage and measuring the d.c. current through it. The ratio of applied voltage and measured current is the armature resistance. But due to the skin effect, the effective resistance under a.c. conditions are more than the d.c. resistance. Generally the effective armature resistance under a.c. conditions are taken 1.25 to 1.75 times the d.c. resistance.

While measuring the armature resistance, it is necessary to consider how the armature winding is connected whether in star or delta. Consider a star connected armature winding as shown in Fig.

When the voltage is applied across any two terminals of an armature winding, then the equivalent resistance is the series combination of the two resistance of two different phase windings,

...RRY= Resistance between R-Y terminals
= Ra + Ra = 2Ra
where Ra = armature resistance per phase
Ra = RRY/2 Ω/ph
Thus in star connected alternator, the armature resistance per phase is half of the resistance observed across any two line terminals.
Thus per phase DC armature resistance is half of the measured value

Ra = 5/2 = 0.25Ω

94.The d.c. armature resistance of a delta connected alternator measured across its two terminals is 1 Ω. The per-phase d.c. resistance is

3 Ω

0.33 Ω

2 Ω

1.5 Ω

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Consider the delta connected alternator as shown in Fig.

When the voltage is applied across any two terminals, then one phase winding appears in parallel with the series combination of the other two.
Hence the equivalent resistance across the terminals is the parallel combination of the resistance Ra and 2Ra.
 

 
Therefore, per phase d.c. armature resistance is
 
Ra = (3 × 1) ⁄ 2 = 1.5Ω

95.Which of the following graph represents the speed-torque characteristics of a synchronous machine.

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For cooling of large size generators hydrogen is used because

It offers reduced fire risk

All option are correct

It is of high thermal conductivity

It is light in weight

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96.The advantages of the parallel operation of the alternator are

Ease in the future extension

Increase Efficiency

All option are correct

Maintained continuity of supply

The demand for power is increasing day by day. It is a challenge for power engineers to meet the power demand of customers. A single alternator cannot meet the power demand. To meet the excess power demand, additional alternators are connected in parallel. If a single alternator can meet the power demand, an outage of the alternator will cause an interruption of power supply. On the other hand, the paralleling of alternators ensures the supply of a part of the total demand when one alternator is out of order.



Reasons for Paralleling of Alternators

The reasons for paralleling are
A single alternator may not meet the local or regional power requirements.</li
It is possible to shut down one or more alternators for scheduled or emergency maintenance when the alternators are operating in parallel. The load can be supplied.
At part load, one or more alternators are shut down and the remaining load is carried out with few machines efficiently because alternators are inefficient at part load.
It is possible to handle load growth by adding alternators without disturbing the original installation.</li
The available machine prime movers and alternators can be matched to obtain economical cost and reliable use.


Advantage of Parallel Operation of Synchronous Generators
The following are the advantages of connecting a large number of synchronous generators in parallel to supply a common load:

Continuity of Supply and Maintenance: Repair and maintenance of individual generating units can be done keeping the continuity of supply by properly scheduling maintenance of generators one after the other. If only one large generator is installed, supply is to be cut off for maintenance work.
Efficiency: For operating an alternator on maximum efficiency it is to be run near to its full-load capacity. It is uneconomic to operate large alternators on low loads. If several small units are used. units can be added or put off depending upon the load requirement and thus the units can be operated near to their rated capacity.
Capital Cost:  Additional sets can be connected in parallel to meet the increasing demand, thereby reducing the initial capital cost of buying larger units in anticipation of increasing demands.
Size of Alternators: There is the physical and economic limit to the possible capacity of alternators that can be built. The demand for a single power station may be as high as 1200 MVA. It may not be feasible to build a single alternator of such a high rating due to physical and economic considerations.

97.A 50Hz synchronous generator is initially connected to a long lossless transmission line which is open-circuited at the receiving end. With the field voltage held constant, the generator is disconnected from the transmission line. Which of the following may be said about the steady-state terminal voltage and field current of the generator?

Both magnitudes of terminal voltage as well as field current remain same

The magnitude of terminal voltage decrease but field current remain the same

The magnitude of terminal voltage decrease and field current increase

The magnitude of terminal voltage increase and field current decrease

As field voltage is held constant therefore field current does not change or remain constant. When the generator is connected to an open-circuit transmission line, the line draws charging current, therefore V_t  > E_g. But, when the generator is disconnected from the line, no charging current is delivered by the generator, i.e., Ic = 0 ⇒ V_t  = E_g. So, the terminal voltage decreases. or A long transmission line under no-load condition behaves as the capacitive load. The effect of armature current purely magnetization. When the alternator is disconnected, there is no magnetizing effect. So the terminal voltage decreases with the same field current.

98.A field excitation of 20 A in a certain alternator results in an armature current of 400 A in short circuit and a terminal voltage of 2000 V on open circuit. The magnitude of the internal voltage drop within the machine at a load current of 200 A is

10 V

1 V

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100 V

1000 v

Given

Field excitation If = 20 A 
Short circuit armature current Isc = 400 A
Open circuit terminal voltage Voc =  2000 V
Load current IL = 200 A

Generated voltage per phase of an alternator is given as

Ef = Vt + ILRa + ILXL
If the armature resistance is neglected than Generated voltage

Ef = VPH + ILXL

For a given field current, under short circuit condition

Ia = Isc; Vt = 0
∴ XL = Ef ⁄ Isc--------------(1)

For open circuit
Ef = Voc ; Ia = 0
Putting the value of Ef in equation 1 we get
XL = Voc ⁄ Isc

= 2000 ⁄ 400 = 5Ω

Hence Internal Voltage Drop = Ia × XL
= 200 × 5
= 1000 V

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99.A three-phase alternator has a negligible stator resistance. A short-circuit test is conducted on this alternator. At a particular speed, a field current of is required to drive the rated armature current. If the speed of the alternator is reduced half, the field current required to maintain rated armature current

14%.

− 8.9%

0%

 7%.

No Load Induced Voltage of Alternator "E" is given as

---

100.Why is hydrogen used for Alternator cooling?
Hydrogen is the least expensive, with less weight, high thermal conductivity, less density, and less viscosity. Less weight, less density & less viscosity attributes to its flow rate. High thermal conductivity helps in better heat exchange. Least expensive helps in balance sheets, more power in fewer investments.

In order to reduce the high temperature of alternator hydrogen gas is used as a coolant. The coolant, Hydrogen gas is allowed to flow in a closed cyclic path around the rotor. Heat exchange takes place and the temperature of hydrogen gas increases, for better cooling of the rotor in the next cycle it has to be cooled. Cooling of hydrogen gas is done by passing it through heat exchangers generally constituted with water. Now Hydrogen gas after cooling is allowed to pass through driers ( mainly silica gel which absorbs moisture) and allowed to pass again through the rotor.

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