Electrical Engineering Aspect

 Series and Parallel Circuit:
1. Series Circuit:
A simple circuit or path of any complex circuit in which same current passes through all the elements in that path is called series circuit. The general circuit diagram of series circuit using resistors is as shown as follows. Series circuit have following features.
- Same current passes through all the element.
i.e. I₁ = I₂= …………………… = I_N = I
- Voltage divides in all the components. So, It is known as voltage divider circuit.
i.e. V = V₁+ V₂+ …………… + V_N

i.e. Voltage across ith component is,V_i = (R_i/n)× V = {R_i/R_eq}× V
- Equivalent resistance of series circuit is given by sum of all the components.R_eq = R₁+ R₂+ …………….. + R_N

Note : For multiple number of inductors in series:
L_eq = L₁+ L₂+ ……………………….. + L_N 

For multiple number of capacitors in series
- If one components failsin performing it’s operation in series circuit, it cause failure of overall circuit due to opening of single path.
2. Parallel circuit :
When potential different across any two paths or components is same, those two paths or components are said to be parallely connected. The general circuit diagram of parallel circuit is as shown as follows.
Parallel circuit have following features :
- Current divides through different element so it is known as current divider circuit. Current in ith component is given by,
- Applied voltage across each elements remains same.
i.e. V₁= V₂ = V₃ = ………………. = V_N
- Equivalent resistance of parallel circuit is given by the formula.
Note : For multiple number of inductors in parallel
For multiple number of capacitors in parallel
Ceq = C₁+ C₂+……………… + C_N
- If one component fails in performing its operation in parallel circuit, it does not cause failure of any other circuit operation.
 

2. Energy Resources
Energy Resources are classified as follows.
- Renewable & Non-Renewable Resources
Renewal Resources :
They are not depleted and available in long term in periodic basis.
a) Biomass : Different types of plant materials which contains stored energy that comes from sun are called biomass. e.g. Gobar gas, wood, coal etc.
b) Solar energy : It is the form of energy which applies energy from the sun in form of solar radiation. e.g. Solar power, photovoltaic output energy.
c) Wind Energy : It is conversion of wind energy into a useful form of energy. e.g. Wind turbine and generator Output in electrical power, wind mills output in mechanical power.
d) Hydropower : power generated from energy in water is hydropower. e.g. Hydroelectricity.
e) Geothermal Energy : Energy from thermal energy generated and stored in the core of earth.
f) Ocean & Tidal Energy : They are generally those forms which generate electricity from the tides in the ocean.
g) Biofuel : Energy derived from biological carbon fixation. e.g. Biomethanol, Biodiesel etc.
Non Renewal Resources :     
They are depleted with continuous use.
a) Fossil Fuel : Fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. E.g. Coal, Petrolium and natural gas.
b) Radioactive fuel/ Nuclear commercial Resources : Energy generated from nuclear reaction of radioactive material.
 

ii. Commercial and Non commercial Resources
Commercial Resources : They are useful for commercial processing purposes. e.g. Coal, Petrolium, Natural gas, Nuclear Energy, energy derived through thermo chemical and biochemical process etc.
Non commercial Resources : They are abundant in nature and are mostly used in rural area e.g. cowdung, charcoal, firewood, agricultural waste.

iii. Conventional and Non conventional Resources
Conventional Resources :
The sources of energy which have been in use for a long time. e.g. coal, petroleum, natural gas and water power.
Non conventional Resources :
The resources which are yet in the process of development over the past few years : e.g. solar, wind, tidal, biomass, biogas, geothermal.

3. Transformers :
- It is static electric machine which transfers electrical power from one circiut to another without changing frequency.
- It works on the principle of mutual induction.
- Parts of transformers.
a) Primary winding : Where input is given
b) Secondary winding : Where output is taken
c) Core : On which primary and secondary windings are wounded.
d) Yoke : Horizontal part of transformer core
e) Limb : Vertical part of transformer core
- It doesn’t work with DC source.
- Soft iron is used for making transformer core because of its high permeability.
- Transformation ratio (K) = N₂/N₁ = V₂/V₁ = I₁/I₂ 
a) If K = 1, N₁= N₂ (isolation transformer)
b) If K > 1, N₁< N₂ (step-up transformer)
c) If K < 1, N₁> N₂ (step-down transformer)
- Rms value of emf, induced in secondary winding is, E₂= 4.44fϕm
N₂
- Ideal transformer is that which has
a) No winding resistance
b) Core with infinite permeability
c) No coreloss and 100% efficiency.
- Eddy current is current circulating within core.
- Eddy loss α (I_eddy)².
- Copper loss in transformer is loss in winding resistance.
- During transformer operation, frequency remains constant.
- Core of transformer is laminated by varnish to reduce eddy current current loss.
- Capacity of transformer is measured KVA.
- Transformers are classified into three types according to utilities.

a) Power transformer :
• May be step-up or step-down (i.e. K >1 or K< 1).
• Rating is above 200 KVA.
• They are used at stations and substations.
b) Distribution transformer :
• They are step down (K<1).
• Used for consumer purposes.
• Rating upto 200 KVA.
c) Instrumental transformer :
• They are used for measurement purpose.
• CT (current transformer) is used to measure very high current.
• PT (potential transformer) is used to measure very high voltage.
 

4.Electrical Energy Generation
- It is based on the fundamental principles of electricity generation discovered by Michael Faraday.
- If Bm is maximum flux density, v is velocity of rotating coil, L is length of coil and ϕ is angle between axis of uniform magnetic field and axis of uniform magnetic field and axis of coil, magnetitude of induced emf is
E = BmLV sinϕ

Electricity Generation:
i. Convential methods of power Generation:
(They make use of prime mover for dividing electrical machines) e.g. Thermal, Hydro, Nuclear, Solar power generation etc.
ii. Non convential Methods of power Generation:
(They donot involve prime mover for power generation) e.g. solar cells, fuel cells, thermo electric generation etc.
 

Instrument In Electrical Measurement:
- Ammeter is used to measure current current through any element.
- Ideal ammeter has zero internal resistance.

- Ammeter is always connected in series with the element through which current is to be measured.
- Voltmeter is used to measure potential difference between two points of circuits.
- Voltameter is always connected in parallel with the element across which p.d. is to be measured.
- Ideal voltmeter has infinite resistance.
- Instrument voltmeter has infinite resistance.
- Instrument used to measure active electrical power is wattmeter i.e. It measures active power only i.e. VIcosφ.
 It has current coil which measures current (I) and voltage coil which measures p.d.(v) across  any element.

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Computer and Electronics Engineering Aspects

Types of number system:

1.       Binary number system; base ‘2’

Digits used = 0, 1 eg. (100011)₂.

2.       Octal number system; base ‘8’

Digits used = 0 to 7. eg. (352674)₈.

3.       Decimal number system; base ‘10’

Digits used = 0 to 9. eg.(86459)₁₀.

4.       Hexadecimal number system; base ‘16’.

Digits used = 0, 1, 2, 3, 4, 5, 6, 7 , 8, 9, A, B, C, D, E, F. eg.(64F32B45A)16.

Conversions with examples:

1.       Decimal to Binary:

2.       Decimal to octal:

 

-        The smallest unit of data on a binary computer is a “bit” (1 bit = 0 or 1).

-        Nibble is a collection of 4 bits.(1 nibble = 4 bits).

-        Byte consists of 8 bits. (1 Byte = 8 bits).

-        Diode can convert AC into DC but not DC into AC.

-        At absolute zero temperature semiconductor acts as an insulator.

-        Semiconductor have negative temperature coefficient of resistance.

-        When a diode is into non conducting state has a very high resistance.

-        An electrical device allowing current to move through it in one direction is called diode.

-        The term ‘diode’ is customarily used for small signal devices. I<1A.

-        The term ‘rectifier’ is used for power devices, I>1A.

-        The diode is said to be forward biased, when voltage is supplied across is diode in a way that it allows current to flow.

-        The diode is said to be reversed biased, when voltage is supplied across a diode is in a way that it prohibits the flow of current.

-        Silicon and germanium diodes have a forward voltage of approximately 0.7 and 0.3 volts.

-        Zener diodes are used as voltage regulators.

-        Photo diode is used to convert light signal into electrical signal.

-        LED converts forward current into light.

-        Varactor diodes are used in tuning a radio station, TV channel or in telecommunication, etc.

-        The bipolar junction transistors is a three layer sandwich of P-type and N-type semiconductors. The three layer may be arranged in PNP or NPN order. According to this order, there are two transistors.

PNP transistors

NPN transistors

-        An electronic/digital circuit which has one or more inputs but only one output is called logic gate.

-        A table which gives the input-output relationship of the binary variables for each gate is called truth table.

-        AND gate gives a high output(1) only if all its inputs are high. It is represented by A.B.

-        OR gate gives high output(1) if one or more of its inputs are high. Represented as A + B.

-        NOT gate is also known as an inverter.If the input variable is A, the inverted output is known as NOT gate. Written as A’ or Ᾱ.

-        EXOR (Exclusive OR) gives high output if either but not both of its to two inputs are high. It is represented as A⊕B.

Basic computer:

- Types of computer:

A.      On the basis of operation:

i.        Analog computer: Eg. Thermometer

ii.       Digital Computer: Eg. Laptop

B.      On the basis of uses:

i.        General purpose computer

ii.       Special purposes computer

C.      On the basis of capacity:

i.        Super computers

ii.       Minicomputers

iii.      Macrocomputers

-        The first electronic computer was ENIAC.

-        The first micro computer was IBM-PC.

-        The first micro processor was designed by INTEL.

-        SRAM – stands for “Static Random Access Memory.”

-        DRAM – stands for “Dynamic Random Access Memory.”

-        PROM – stands for “Progammable Read Only Memory.”

-        EPROM – Erasable Progammable Read Only Memory.

-        EEPROM – Electrically Erasable Progammable Read Only Memory.

-        Input devices : Keyboards, Mouse, Touch, Pad, Joystick, Track ball, Digital camera, etc.

-        Output devices : Monitor, Printer, Plotter, etc.

Types of operating system :

i.        Muti user : eg. MVS, UN’X

ii.       Multi programming : eg. windows 95, windows NT, UNIX,windows 3.X.

iii.      Multiprocessing : eg. MVS, UNIX.

iv.      Multithreading :

v.       Real time : eg. P-855, P-860.

-        MS-DOS doesn’t support long file names.

-        Key ingredient of processor is transistor.

-        Speed of CPU is determined by no. of transistor.

-        CRT – Cathode Ray Tube.

-        OCR – Optical Character Recognition.

-        MBR – Master Boot Record.

-        FAT – File Allocation Table.

-        FTP – File Transfer Protocol.

-        ISP – Internet Service Provider.

-        WWW – World Wide Web.

-        USP – Un-interruptible Power Supply.

-        MODEM – Modulator Demodulator.

-        VGA – Video Graphics Array.

-        E-mail messages are usually encoded in ASCII ext.

-        The capacity of a standard PC floppy is 1.4448.

-        1 KB = 1024 bits.

-        1 MB = 1024 KB.

-        1 GB = 1024 MB.

-        1 TB = 1024 GB.

-        The capacity of cache memory is 4 MB.

-        The capacity of Magnetic disk is 200 – 1000 GB.

-        TEL NET is used for remote login

-        MODEM converts digital date to analog and vice versa.

-        IP is distinct for each computer network.

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Civil Engineering Aspect

1. Cement :
- It is prepared by heating lime (CaO), Clay (Al₂O₃.SiO₂) and gypsum (CaSO₄.2H₂O)
- Functions of different constituents
a. Lime: it makes cement strong.
b. Clay : It provides strength and quick setting property to cement.
c. Gypsum : It regulates hardening time of cement.
- Cement contains (⅔)rd lime stone and (⅓)rd clay.
- When water is added to grinded mixture of lime and it is called slurry.
- Cement clinker is mixture of calcium aluminates and calcium silicates. It is hard grayish particle.
- A thick paste of cement and water is called mortar.
- Strength of cement is measured in its compressive strength which is expressed in mega pascal (MPa).
- Most commonly used cement is Ordinary portland cement (OPC).
- Cement is binding material in concrete.
- Clinker is formed around at 1500°C.
- Volume of 1 bag cement is 0.035 m³.
- In cement mortar 1 : 4 indicates the ratio of cement and sand.
- Normal bag of cement has weight of 50 kg.
2.    Aggregate :
- Gravels crushed stone and other materials that are mixed with cement and water to make concrete is called aggregate.
- Durability and cleanness is essential requirements of aggregate.
a.     Fine aggregate : Which passes through 5 mm B.S. sieve. e.g. natural sand.
b.     Coarse aggregate : Which are completely retained on 4.75 mm sieve. e.g. crushed rock.
- Sand is fine aggregate.
- Initial increase in volume with increase in moisture content of sand is called bulking of sand.
- Bulking is more in finer sands than in coarser ones.
3.    Concrete :
- Mixture of cement, sand, gravel and water is called concrete.
- W/C indicates water to cement ratio. Increase in W/C ratio decrease the strength and durability of hardened concrete.
- On increase A : B : C indicates ratio of cement, fine aggregate (sand) and coarse aggregate.
- Hydration is responsible for strength of cement particles.
- Water curing is done to reduce the heat generation during hydration in concrete.
- Comprehensive strength of concrete is determined after 28 days of curing.
- Concrete contain rod is called Reinforced Cement Concrete (RCC).
4.    Building Stone :
- Generally rocks in the crust of earth are processed to give the building stones.
- The porosity of good building stone should be less than 5%.
- Classification of Rocks :
i. Geological Classification :
a.  Igneous Rocks : Rocks formed by cooling and solidification of magma (hot viscous liquid within earth crust) are igneous rocks. e.g. granite, dolomite, basalt, etc.
b. Sedimentary Rocks : Rocks formed by deposition of existing rocks because of weathering action of water, wind, frost, etc. are sedimentary rocks. eg. gravel, sandstone, limestone, etc.
c. Metamorphic Rocks : When igneous rocks and sedimentary rocks undergoes into changes in their constitution is called metamorphic rocks. eg. gnesis, slates, etc.
ii. Physical Classification :
a. Stratified rocks : Rocks with layered structure in their natural form. eg. sandstone, limestone, slate, etc.
b. Unstratified rocks : They donot contain strata or layer in them. Eg. granite, marble, trap, etc.
iii. Chemical Classification :
a. Silicious Rocks : Rocks containing silica as their main component. Eg. sandstone, trap, granite.
b. Argillaceous Rocks : Rocks containing clay or alumina as their main components. Eg. slates, laterite, etc.
c. Calcareous Rocks : Rocks containing calcium carbonate as their main component. Eg. marble, limestone, etc.
5. Bricks:
- Bricks are clay products.
- They are derived by disintegration of igneous rocks.
- Al₂O₃.2H₂O is commonly known as kaoline.
- Brick composition
                 i.   Clay : 20-30% by weight.
                ii.   Silt : 20-35% by weight.
                iii.   Sand : 35-50% by weight.
- Red colour of brick is due to oxide of iron.
- Clay or Alumina makes brick hard.
- Silica or sand in brick prevents shrinkage and cracking of bricks.
- Pebbles of stones and Gravel, Alkaline salts, Limestone & kankar and vegetation and organic matter are harmful ingredients of brick.
- Standard size of common building bricks is 230mm × 110 mm × 55 mm.
- Strength of brick is measured in N/mm² or MPa.
- First class bricks has compressive strength not less than 10.5 MPa.
- Efflorescence is due to sulphates of sodium and potassium present in brick.
- The weight of common bricks was varies from 1600-1920 kg/m³.
- The number of bricks required per cubic meter of brick masonary is around 500.
- Clay is burnt at 1000-1200°C at kiln to prepare bricks.
- Black cotton soil is very good for making bricks.
6.    Traffic Sign :

=> The main function of traffic sign is to regulate, warn and inform.
1.       Red signal – To stop the traffic : Bring your vehicle to a complete halt behind the stop line or crass walk. Wait until the light turns green.
2.    Amber/Yellow signal – caution : If you have entered the intersection and the light turns to amber/yellow, move on carefully. If you see the light before entering the crossing, stop the vehicle behind the stop line or cross walk.
3.    Green signal – Go on : Go through the the crossing carefully. You can turn in the direction of the arrow by giving indicator.
•      There are three groups of traffic signals.
 i. Regulatory signs/Mandatory-order & Regulation sign :
-    They are prohibitory (what drivers must not do) and mandatory (what drivers must do) types of signs.
-    Most of them are in form of circular disc.
ii.  Warning signs (Dangerous and warning signs):
-    They warn drivers of some danger or difficulty on the road ahead.
-    They are in form of an equivalateral triangle.
iii.   Information signs :
-    They give information to drivers to find their way to their destination.
-    They are in form of either square or rectangular in shape.
 iv.   Pedestrian signals :
These signals help pedstrains to cross intersections safely.
• Steady Red human figure → Donot enter the road.
• Flashing signal → Cross the road quickly.
• Steady Green human figure → walk cautiously.

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Mechanical Engineering Aspect

Engines :

1. Classification:

(a) According to type of used, they are classified into petrol Engine, Diesel engine and Engine.

(b) According to number of strokes required to complete the cycle, they are classified into four stroke and two stroke engine.

Four stroke : Cycle completes in two revolution of crankshaft.

- There is one power stroke in every four strokes.

Two stroke : Cycle completes in one revolution of crankshaft.

- There is one power stroke in every two in every two strokes.

(c) According to cycle of operation, they are classified into two types.

Otto cycle :- Combustion of fuel takes place at constant volume. Eg. petrol engine, gas engine.

Diesel cycle :- Combustion of fuel takes place at constant pressure. Eg. diesel engine

(d) According to methods of ignition, they are classified into types.

Spark Ignition Engine :- The mixture of fuel and air is ignited with the help of an air is ignited with the help of an electric spark. Eg. petrol engine.

Compression Ignition Engine :- Fuel is ignited with the help of compressed hot air. Eg. Diesel engine.

(e) According to method of cooling, they are classification into two types.

Air cooled Engine :-Cooling is provide by air. Eg. Scooter and motor engine.

Water cooled Engine :- Cooling is provided by water. Eg. bus and truck engine.

(f) According to method of governing used, they are classified into two types.

Quality Governing :- Air-fuel ratio is constant but air and fuel content can be changed. Eg. petrol engine.

Quantity Governing :- Air-fuel ratio is not constant but air and fuel content changed as per requirement. Eg. diesel engine.

2. Comparison of two stroke and four stroke :

· Two stroke engine develops 1.7 to 1.8 times the power developed by four stroke engines as some power is used for compressing the charge in crank case and due to scavenging.

· Two stroke engine is lighter, less bulky and occupies less floor area then 4-stroke engine.

· The torque is uniform in two-stroke engine compared with four stroke engine so it requires lighter flywheel and lighter foundation.

· Two stroke engine is mechanically simpler.

· Two-stroke engine has higher mechanical efficiency.

· The starting of two-stroke engine is easy compared with four-shaped engine.

· The weight per H.P. capacity of two-stroke engine is less than four-stroke engine.

· The overall efficiency of two-stroke engine is less than four-stroke engine as some charge is lost to atmosphere during scavenging.

· The fuel consumption per kilometer and the running cost of two-stroke engine is higher than four-stroke engine.

3. Petrol Engine :-

· A four stroke petrol engine has four strokes such as suction stroke, compression stroke. Expansion stroke and Exhaust stroke.

·Air fuel ratio is controlled by carburettor in petrol engine. Air ratio is ratio is generally 15 : 1.

· The compression ratio in compression stroke of petrol engine is 6 : 1 to 10 : 1.

· Thermal efficiency of petrol engine is 25% to 30%.

· Compressed fuel and air mixture is ignited with the help of electric spark at the beginning of expansion stroke, so it is commonly called as spark ignition engine.

4. Diesel Engine :-

· During suction only air is taken inside the cylinder.

· Compression ratio of diesel engine varies from 14 : 1 to 25 : 1.

· Thermal efficiency of Diesel engine is about 65% to 70%.

· Diesel is sprayed just before completing the compression stroke, diesel is burnt with the help of hot, compressed air, so it is also known as compression ignition Engine.

5. Different terms of IC (Internal Combination) Engine :-

i. Indicated Horse Power (IHP) :-

- Power developed inside the cylinder of an IC engine.

ii. Brake Horse Power (BHP) :-

- Power available at the shaft of an IC engine.

- This power gives the output to drive the load.

iii. Frictional Horse Power (FHP) :-

- It is loss of power while transferring from cylinder to shaft.

- FHP = IHP - BHP

iv. Indicated Thermal Efficiency (η_i):-

(η_i)= IHP/(heat supplied to engine)

v. Brake Thermal Efficiency (η_b):-

(η_b)= BHP/(heat supplied to engine)

vi. Mechanical Efficiency (η_m):-

(η_b)= (BHP/IHP)= (η_b)/(η_i)

6. Renewable and Non-Renewable Energy Resources :

i. Renewable energy Resources :- They are not depleted and available in long term in periodic basis. Eg. Biomass, Solar Energy, Wind Energy, Hydropower, Geothermal Energy, Ocean Tidal Energy Biofuel, etc.

ii. Non-Renewable energy Resources :- They are depleted with continuous use. Eg. Fossil fuels, Radioactive fuel/Nuclear Energy, etc.

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