Solar Energy Collectors, Types of Solar Energy Collectors

In this article we will know about the solar energy collectors . we also know about the types of solar energy collectors.

Solar Energy Collectors

The first step in the solar energy utilization is the collection of this energy. This is done through collectors whose surfaces are designed for high absorptive and low emissivity.
Solar energy collectors, types of solar energy collector
these are following types of solar energy collectors. which is shown below.

1.  Flat Plate Collector.

 A flat collector consists of the following basic element:. it is very efficient type solar energy collector.
1. A flat plate upon which the short wave solar radiation falls and is absorbed and converted into heat energy.

2. An insulated container to eliminate or substantially reduce thermal losses from the collection system.

3. One or more plates of glass or transparent plastic to reduce the upward heat loss from the collection surface.

 4. Tubes or channels to circulate the liquid required to remove the heat energy from the collector to the strong tank.

A flat plate collector is shown in Fig. Solar radiation passes through the transparent cover and is absorbed by the collector plate. A fluid flowing in a passage in contact with the collector is heated and the heat from the fluid is extracted for use. The circulating pump keeps a continuous circulation of the fluid through collector and strong tank. In the storage tank, is working as heat ex changer, fluid heats water which is used for the desire purpose. The efficiency of the collection and conversion process depends on the heat loss to surroundings which in turn depends on the temperature at which the collectors work. The cover plate is transparent to incoming radiation but opaque to infra red radiation of the collector and thus reduces the heat losses. Treating the collector surface with special coating reduces the heat losses still further. These coating can be
 (1) particles of copper oxide about 1 u m in diameter, 
(2) semi- conductor like silica 
(3) layered coatings of calcium oxide and magnesium oxide. 

These coating have a high ratio of absorptive emissivity (about 10 to 15 or so) but are very expensive. Al though a variety may be used for the heat transfer in the collector flow channels. All practical system to date have used water or water ethylene glycerol solution, the letter additive being used primarily to avoid problem due to the freezing of liquid in the tube under subzero temperature conditions. it is very simple and less costly type solar energy collectors.
Solar energy collectors, types of solar energy collector
 Flat plate collector with honey comb structure. There is a growing interest in the use of honey comb cellular structure of various shapes. Some of which are shown in fig. 15.8.their excellent strength to weight ratio they have many application in aircraft and aerospace industries. Many materials like aluminum, glass, plastics etc. are used in the manufacture
Of these structures. It has found that collectors with honey comb cellular structures are more efficient and their use has been proposed in solar heat collectors. The process of heat transfer is a multi mode phenomenon and all the three modes, conduction, con- vection and radiation, should be considered in assessing the overall performance of any structure. In term of conduction affect the cellular surface. May be envisages as an extended surface used to increase the heat transfer area. In terms of convection effects, structure has been found to modify the convection transport from a heated body and in terms of radiation effects, they have been proposed for the creation of artificial black bodies and specials forms of terminal traps. An inclined flat plate solar collector with honey comb structure is shown in diagram.

2.  Concentrating Collectors

 In spite of the methods of reducing heat losses the maximum temperature at which a flat plate collector works is quite low, around 100 C IN summer and around 40c in winter. Concentrating collectors are more effective but very closely. Parabolic- at around can be   reflector used up to 30000 c However its direction has to be adjusted to follow the direction of sun rays.

A hemostat (b) is often used to reflect the radiation directly on the object to be heated. A combination of heliostat and parabolic reflector may also be used. The heliostat reflects the sun’s rays to the reflector. The heliostat can be adjusted to account for the change in sun’s position. it is very useful type solar energy collector .
Solar energy collectors, types of solar energy collector
The reflective surface of a heliostat usually consist of back silvered low iron glass or metalized plastic. These are fixed to light and mechanically stiff back up structures. The reflective surface is generally made up several small segments to allow better control of the flatness than a large single surface. These segments are also easily replaced in case of damage. The heliostats elements are mounted on that are fixed perpendicularly to a horizontals elevation members. Azimuth ally are elevations movements are made by separated drive mechanisms which typically consist of electric motor driven gears connected to the axes.

Helios tats have been found to be very suitable as collectors for solar power plants. Their cost is one of the key costs in the total cost of the plant. It is expected that better manufacturing processes and mass production will reduce their cost. hence it is main type of solar energy collector.

 SOLAR PONDS. 

Non-convective solar ponds have been suggested for collecting solar energy on a large scale. A solar pond is a shallow body of water, about 1 metre deep containing dissolved salts to generate a stable density gradient (fresh water on top on denser salt water at bottom). Some of the incident solar energy entering the pond surface is absorbed throughout the depth and the remainder which penetrates the pond is absorbed at the black bottom. If the pond had only fresh water (or water of the same density) the lower layers would heat up, expand and rise to the surface. Because of convective maxing and heat loss at the surface only a small temperature rise in water would be realized. The convection can be eliminated by initially creating a sufficiently strong salt concentration gradient. In this case the thermal expansion in the bottom lower layers is insufficient to destabilize the pond. With convection nearly eliminated the heat loss from the lower layer is only by conduction. Because of its relatively low thermal conductivity water acts as insulator and permits temperatures up to 90%c to be developed in the bottom layers. solar pond is use full for solar energy collector to produce electricity,

Solar energy collectors, types of solar energy collector

One way to extract heat from solar ponds is to place pipes in the lower layers and circulate water through these pipes. A simpler and more efficient approach is to take advantage for stable density stratification and use method of selective withdrawal, a technique often use for water quality control in large reservoirs. A sink placed in stably stratified liquid withdraws the liquid from a thin horizontal layer, just as one would draw a single card from a deck. This flow is quite different from one that would occur if the density of water were the same throughout. The phenomenon of selective withdrawal provides means by which, firstly, the stable density gradient required in the upper insulating layer can be corrected and maintained at secondly the hot lower layer can be removed, passed through a heat ex changer and returned at a lower temperature to the bottom of the bottom of the pond. It is sometimes desirable to separate physically the bottom layer from the upper layer by a thin zone transparent partition, generally made of plastic.

The use of solar ponds has been suggested for salt production, space heating and power generation using organic fluid Rankin cycle engines which can operate relatively low source temperatures.  

Hence these are solar energy collector if you find any incorrect in above article you must comment below in comment box.

If you want to know more about the solar energy collectors you must watch this video.


Photo-Voltaic Cell Working

 In this article we will know about the photo-voltaic cell working and their application . we will know brief working of photo-voltaic cell.

Photo-Voltaic Cell working
It is possible to covert solar energy directly into electric energy by photo-voltaic process. The photo-voltaic effect is the generation of an EMF as a result of the absorption of ionizing radiation. Energy conversion devices which are used to convert sunlight to electricity by photo-voltaic effect are known as photo voltaic cells. Thus a solar cell is a transducer which converts the sun’s radiant energy directly into electricity and is basically a semi conductor diode capable of developing a voltage of 0.5 -1v and a current density of 20-40mA per 2cm depending on the materials used and the sun light conditions.

The photo –voltaic effect can be observed in nature in a variety of materials but the materials having the best performance in sun light are the semi conductors. When photons of the sun light are absorbed in a semi –conductor, they create free electrons (and holes) with higher energies than the electrons which provide the bonding in the crystal. Once these free electron holes to flow pairs are created, there must be an electric field to induce these higher energy electrons and holes to flow out of semi conduction to do useful work. In typical solar cell this is done by the use of p---n junction. It is known that an electric field exists across a p—n junction and this field sweeps the electrons in one direction and holes in the other. so these are basic working of photo-voltaic cell.

A typical solar cell is shown in diagram.  active area of solar cell is less than full front surface area because of the need to position opaque conductors on top the cell to collect the generated current. Practical top contact structure are generally in the form of comb to like grids so designed as to strike a balance between reduced active area and reduced series resistance brought about the increasing the contact coverage. An anti reflection coating is often employed to improve the coupling of light into the semi-conductor. The solar cell has to be encapsulated to protect it from atmospheric degradation.so it is overall working of photo voltaic cell. for better know about photo-voltaic cell we must need to know about working of solar cell.

 Solar cell working

 Many types of solar cells have been proposed. The two types available commercially are single crystal silicon cells and cadmium sulfide/cumbrous sulfide cells. Single crystal silicon is the most highly developed material for photo voltaic conversion. The physical properties of single crystal silicon are well understood and the raw material is abundant. Single crystal silicon cells have efficiency around 10to 14 per been used for many years as power sources for space craft in sizes from a few watts to over 20KV per satellite. However they are still very costly and many attempts have been initiated in France, Japan, USA, West Germany etc. to reduce the cost.
    Hence these are photo-voltaic cell working if you will find any incorrect in above article you must comment below in comment box. thanks
If you want to know more about the photo voltaic cell working you must sea this video.

Conversion of Solar Energy into electrical Energy

In this article we will know that how solar energy converts into electrical energy, we will know about the conversion of solar energy into electric energy.

 SOLAR POWER PLANT

A solar power plants coverts solar energy into electrical energy. It consists of the following sub- systems.
  1. Solar energy collection system
  2. Thermal energy transfer system
  3. Thermal energy storage system
  4. Energy conversion system.

 Conversion of Solar Energy into electrical Energy 

A number of designs for the above sub- systems have been proposed. However only two types of solar power plants have been found to be feasible. These are known as Solar Farm or Distributed Collector system (DCS) AND Solar tower or central receiver system. The sub-system for the (DCS) having the following main features and details.
Conversion of Solar Energy into electrical Energy

1.  Solar energy collection system

The solar energy collection system for a DCS may consist of parabolic or parabolic dish collector.


A parabolic trough collector has an axial parabolic reflector at the focus of which is a heat receiver in the shape of tube. The trough is generally made of glass segments hot mould to shape and silvered on the back face. The segments are provided with a backing surface while may be made of metal of fiber glass or concrete. A number of troughs are combined to form a module. The heat receiver system, for troughs collector, consist of a metal tube inside a glass tube. The inner tube is generally painted black to aid heat absorption. The outer tube minimizes losses. Such a collector result in heat transfer medium temperature in the range of 150%c to 350%c and has an efficiency of about 25%c
Conversion of Solar Energy into electrical Energy
The dish of the parabolic dish collector is made of segments of synthetic material (e.g. fiber glass).small mirrored pieces of facets are bonded to the segments with a special adhesive. The receiver system for this collector has the shape of a sphere having a specially coated external. Surface Small diameter pipes run within the wall of the receiver and carry the heat transfer medium. This collector system result in temperature of 200%C 500%C in the heat transfer medium. its very use full for conversion of solar energy into electrical energy.

2. Thermal energy transfer system.

This transfers the heat energy from the receiver to the turbine. Water, sodium, salts gases (air, helium. Hydrogen, ammonia) can be used as heat transfer media.
When the transfer medium is water, steam can be generated directly in the receiver. When the medium is gas, a gas turbine has to be used. When sodium and salts are used for heat transfer, secondary heat transfer circuit is also necessary and the cost is higher. However, when these media are used higher working temperature and pressures can and the heat transfer coefficients are higher.it is first step of conversion of solar energy into electrical energy.

  3. Thermal energy storage system.

 Solar energy is not available all the time. If a solar power plant is working as an isolated plant and is the only source of supply for an area, some from heat energy storage is necessary. One form of storage can be a pressure vessel storing water and steam at a temperature near the boiling point. When steam is extracted, both temperature and pressure in the vessel decrease causing conversion of water into steam. In this storage system into can run only on part load. The thermal storage system can system can also consist of sodium or molten salt. When this storage system is used, two transfer circuits are necessary. However the turbine can operate at full load from such a storage system. it provide continuity of conversion of solar energy into electrical energy.

4.  Energy conversion system.  

 The energy conversion system converts heat energy to electrical energy. The solar heat from the receiver or storage converts feed water into steam which is fed to turbine. The turbine drives the generator. Steam is condensed in the condenser and water return to the boiler for reuse as feed water .The heat of the cooling water of the condenser may be used for subsidiary purposes.  In various image shows the basic element of a distributed collector system solar power plant. in this type solar energy convert into electrical energy.

SOLAR POWER TOWER.

Considerable attention has been given, during the last few years, to solar power tower concept for conversion of solar energy to electrical energy. In this method a central receiver situated at the top of a tower receivers concentrated solar energy reflected from a field of mirrors (or hemostats) which are arranged in some regular manner around the base of a tower. This collection system simulates a very large parabolic on ground. The solar energy collected by the receiver is absorbed by a receiver coolant which gets heated up. The heat of this finally transferred to feed water in a boiler. The feed water gets converted into a steam which drives the turbine. The receiver coolant can be water, liquid sodium, molten, salts or gases like helium or air.
. The complete system consists of a number of sub-systems. The sub-systems are (1) hemostat or collection sub-system (2) receiver/tower sub-system (3) electric power generation sub-system consisting of steam turbine and generator (4) cooling tower sub-system for cooling the water used in condenser for condenser steam (5) master control sub-system for controlling the whole system (not shown in the figure). (6) Storage sub-system. Some form of storage is needed to maintain plant output at a constant level despite solar insulation variations. solar power tower improve efficiency of conversion of solar energy into electrical energy.


Solar power tower technology is about 40 years old. A 10 mw pilot plant was commissioned in 1981 in California (USA). Considerable design and hard hardware expertise exists in USA for using this concept. Many economic, simulation and optimization studies have been undertaken. The results of economic studies are quite encouraging. The environmental problems are minimal and the concept seems to offer lasting solution of energy shortage problem. 

hence these are some processes which is use in conversion of solar energy into electrical energy if you will find any incorrect in above article you must comment below in comment box.

If you want to know more about what is processes of conversion of solar energy into electrical energy you must watch this video.

Power Plant Economics study

In this article we will know about the power plant economics. Which means we will study about which type resources are required for start a new power plant.

Power Plant Economics

1. COST OF ELECTRICAL ENERGY

It is most important factor of power plant economics.
The generation cost per kWh of energy depends. On the cost covering the purpose, installation and erection of equipment, cost of fuel, labor, repair etc, The generation cost can be divided into fixed cost i.e. the cost which depends on the extent of plants investment and financial rates and remain a fixed one irrespective of the amount of energy generated and operating cost which includes the expenditure for fuel, labor, supervision etc. The operating costs of a plant are generally variable in magnitude and depend on the amount of energy produced.

2.  CAPITAL COST OF PLANTS

Capital cost of plant is also a main factor to know about the power plant economics.
The capital cost of a plant includes the preliminary cost, cost of land and other real estate, cost of design and planning, cost of building and equipment, cost of transportation, erection and installation of equipment and overheads etc. the cost of a steam plant located near a river where adequate supply of cooling water is available would be less than that of one in which cooling towers or ponds are needed for cooling water.
Power Plant Economics study, study of power plant economics.
In addition to the costs mentioned above, the capital cost of a hydro-electric plant includes the costs of dam, earth work, excavation,rail head,highways and other civil works and compensation to property owners whose lands would be submerged in the reservoir.
The capitals costs of plants vary very widely even for similar types of plants and depend to a large extent on the market conditions. The range of cost for hydro plants is greater than that for steam plants, the reason being that in case of steam plants, only about 15 percent of the cost is influenced by topographical condition. Whereas in the case of hydro-electric plants, around 75 percent of the cost is affected by these conditions.
In general a large plant costs less per KW of installed capacity than a small one. A plant having a small number of large sexed units costs less than a plant of the same total capacity but having a large number of small sized units. Roughly the capital costs are around Rs. 3000 to 35000 per KW for diesel, gas and steam plants, Rs 4000 to 60000 per KW for hydro-electric plants and Rs. 15000 to 60000 per KW for nuclear plants.

3. Annual fixed cost of power plant

In this topic we will know about total fixed cost in one year of any power plant. We will discuss about the various type fixed cost, which is essential to know for understand of power plant economics.
Components Of power plant
The annual fixed cost of a plant consists of interest, taxes, insurance, depreciation, managerial and general maintenance cost and rate of return.

A. Interest, taxes and insurance.

The capital for setting up the plant may be provided by the government (or the private owner) or acquired through loan form financial institution or acquired by the sale of stuck or bonds or both. The annual interest and dividend gave to be included in the total cost of service. The utility may have to pay various taxes to town, state and federal authorities. However, only the taxes which are a function of the capital investment should be included in the fixed costs and the other taxes should be included in the operating costs.
Every well managed utility has to incur expenditure on insurance against accident to equipment and personnel.  The list of risk and insurance is usually very long. Example, fire, flood, hail, earthquake explosion public liability, workmen compensation etc. the insurance may be obtained from insurance companies or if the enterprise is very big. It may be self-insured. This is done by setting aside a reserve fund, out of earnings, every year. Such an insurance fund is quite district and separate from the depreciation fund.

B. depreciation of power plant

Every equipment deteriorates or depreciates due to wear and tear, corrosion. Weathering etc. in addition, the equipment may become inadequate due to increase in demand or become absolute and may need replacement by a modern one.
It is necessary for the financial stability and safety that the capital of an enterprise must remain intact. When a plant becomes useless, funds must be available to replace it. The methods for calculating depreciation are discussed in section 3.7.

C. Managerial and general maintenance costs.

part of total wage bill of a power plant is constant irrespective of the amount of energy. These costs are proportional to the size of the plant and the equipment and should be included in fixed costs.

D. Rate of return of power plant


An undertaking can be successful only if it earns profit. It is a private limited company and has floated shares or bonds, it must pay a good dividend so that the value of the shares may be high and the undertaking may be successful. Therefore, a certain rate of return on investment should be taken into account in calculating the annual fixed costs.

4. Operating cost or production cost

The operation of a plant means expenses which vary with the extent of operation or the amount of energy produced. such expenses are included in the annual operating costs, the items which constitute operating costs are:  fuel , operating labor, maintenance costs and supplies. in steam, diesel and gas plants,the operating costs form a major portion of total annual cost whereas in hydro, nuclear and solar plants,the fixed costs overshadow the small operating costs. 

(a)      Fuel. 

This is largest item of expense in thermal, diesel and gas turbine stations. The fuel may be in the form of coal, oil, natural gas, wood scrap etc. The cost of fuel depends on the type of fuel, calorific value, availability and freight rates. The annual fuel cost of a station depends on the amount of energy produced, the efficiency of the plant and the unit price of fuel. The fuel cost of station can be anticipated if (i) a realistic load model is known for each future week or month in the planning period (ii) the units are committed to supply load in a manner that reflects actual operating procedures and conditions.

(b)     Operating labor 

 The operation of a plant needs staff and labor. In a steam plant labor is needed for unloading and storing of fuel, disposal of refuse, operation of boiler, prime mover etc. The increasing application of automatic equipment and the increase in unit sizes have reduced the number of men required to operate a plant by a considerable amount. Hydro plant and diesel plants need less labor than steam plants.

(c)    Maintenance cost. of power plant

 Every plant needs preventive maintenance (inspection cleaning repair, overhauling etc.) to keep it in good condition. The maintenance cost can be further subdivided into the cost of material required for maintenance and cost of labor. To estimate the maintenance cost of proposed plant, the information from a similar plant in an analogous situation can be used.

(d)    Supplies. 

This item includes the cost of water for makes up, cooling purposes and general use, lubricating oil and other consumable materials.
Hence this is power plant economics study if you have find any incorrect in above article you must comment below in comment box. 

Difference between Asynchronous and Synchronous counter

In this article we will know about the difference between asynchronous and synchronous counter. We will also study that what is counter basically and their working.


Difference between Asynchronous and Synchronous counter, Synchronous and asynchronous counter

working of synchronous and asynchronous counter

Counter may be asynchronous counter or synchronous counter. A synchronous counter is also named as ripple counter. In asynchronous counter, all the flip-flips are not clocked simultaneously, whereas in a synchronous counter all the flip-flops have some clock. Comparison of synchronous and asynchronous is given table. 
Difference between Asynchronous and synchronous counter

  Asynchronous counter
  Synchronous counter
1. In case of asynchronous counter, all the flip-flops are not clocked simultaneously.
In case of synchronous counter, all the flip-flops are clocked simultaneously.
2. In the case of asynchronous counter, the output of first flip-flop drives the clock for second flip-flop, the output of second drives the third and so on.
In case of synchronous counter , there is no interconnection between output of one flip-flop and clock of next flip-flop,
3. The settling time of asynchronous counter is cumulative sum of individual flip-flops.
The settling time of synchronous counter is equal to highest settling time of all flip-flops. theses are basic difference between asynchronous and synchronous counter.
4. Asynchronous counter is known as serial counter
Synchronous counter is known as parallel counter.
5.Its design and implementation is very simple.
Synchronous counter design and implementation becomes tedious and complex as the number of states increases.
6. Asynchronous counter is slow in speed as compare of synchronous counter.
Synchronous counter is faster in speed as compare to asynchronous counter.

Hence these are some difference between asynchronous counter and synchronous counter. If you will find any incorrect in above article you must comment in comment box.


If you want to know more about difference between synchronous counter and asynchronous counter you must watch this video.

Digital electronics interview questions

In this article we will learn about the digital electronics interview question. Which is mainly asked in various interview.

Digital electronics interview questions, basic digital electronic question

Digital electronics interview questions

Digital electronics interview questions, basic digital electronic question

1. What is meant by radix (or base) of a number system?

Radix or base of number system is the number of digits or distinct symbols it uses to represent various numbers.

2. What is weighted code? Give one example.

In a weighted code the value of a digit in a 4-bit depends on its position such as in BCD code.

3. What is non-weighted code?

In a non-weighted code, no definite weights are assigned to the four digit positions such as in excess-3 code.

4. What is difference between LSB and MSB?

The right most bit of a binary number is called least-significant bit (LSB) while the left most bit of a binary number is known as most-significant bit (MSB).

5. What is meant by BCD code?

BCD code is a decimal system with each digit encoded in its binary equivalent of 4 bits.

6. What is excess-3 code |?

Excess-3 code is derived from the natural BCD code by adding 3(0011) to each coded number.

7. Why hexadecimal code is widely used in digital system?

It is very convenient to enter binary data in a digital system using hex code.

8. What is the difference between binary code and BCD?

BCD is not a number system like binary. It is a decimal system with each decimal digit encoded in its binary equivalent. A straight binary code takes the complete decimal number and represents it in binary while the BCD code converts each decimal digit to binary individually. It is most useful digital electronics interview question because mostly come in interview exam.

9. Explain the use of excess-3 code.

The key feature of the excess-3 code is that it is self-complementing code. It means that 1’s complement of the coded number yields 9’s complement of the number itself. The self-complementing property makes the excess-3 code useful in some arithmetic operations, because subtraction can be performed using9’s complement method and 1’s complement can be easily produced with digital logic circuits by simply inverting each bit.

10. What are the advantages of gray code?

In Gray code, if we go from any one decimal number to the next, only one bit of the Gray close changes. Because of this feature, an amount of switching is minimized and the reliability of the switching systems is improved. Advantage of gray code is main interview question of digital electronic.

11. What is an alphanumeric code?

The codes used for representing letters of alphabet. Punctuation marks and other special characters along with numbers are called alphanumeric codes.

12. What is Boolean algebra?

Boolean algebra is a mathematical system of logic in which truth functions are expressed as symbols are manipulated to arrive at conclusion. It is also maximum asked in digital electronics interview question.

13. What are the basic logic elements?

Basic logic elements are NOT gate, AND gare, OR gate and the flip-flop.

14. What is a truth table?

Truth table is a table that gives outputs for all possible combinations of inputs to a logic circuit.

15. Define the positive logic and negative logic?

If the higher of the two voltages represents a 1 and the lower voltage represents a 0 , the logic is called a positive logic. On the other hand, if the lower voltage represents a 1 and the higher voltage a 0, we have a negative logic.

16. What is pulse logic system?

A logic system in which a bit is recognized by the presence or absence of a pulse is called a pulse or dynamic logic system.

17. What is an inverter?

An inverter is logic gate whose output is the inverse or complement of its input.it is main equipment of digital electronic system which is asked in interview.

18. What is the specialty of NAND and NOR gates?

The specialty of NAND and NOR gates is that they are universal gates and can perform all the basic logical operations.

19. What is associate law?

Associate law is a law of addition and multiplication and according to this law grouping of the variables in the ORing or ANDing of several variables is immaterial and the results obtained are the same.

20. what is minterm ?.

A term containing literals corresponding to all the variables in ANDed terms ORed terms ANDed together.

21. What is maxterm in digital electronic system?

A term containing literals corresponding to all the variables in ORed from is known as a maxterm.

22. what is the difference between canonical form and standard form?

In Canonical form , a Boolean function is expressed as sum of minterms or product of maxterms and is obtained by  reading a function from the truth table. Canonical forms may or may not contain the least numbers of literals because by definition, each maxterm or minterm must contain all variables, complemented or un complemented. In standard form, the terms of function may contain one, two or any number of literals. Standard form is expressed as sum products or product of sums.

23. what is the use of De Morgan’s theorem.?

De Morgan’s theorems are extremely useful in simplification of Boolean expressions in which a sum or product of variables is inverted.

24. What is karnaugh map?

The limitation of karnaughs map is that beyond 6 variables it becomes very cumbersome and so it is generally used up to 6 variables.

25. What is the use of a karnaugh map?

Karnaugh map is used for simplification and manipulation of Boolean expressions.

26. What is a half-adder?

A logic circuit, that can add two 1-bit numbers and produce outputs for sum and carry, is called a half adder.

27. What is full-adder?.

A binary adder, which can add two 1-bit binary numbers along with a carry bit a produces outputs for sum and carry is called a full-adder.

28. What is logic signal required to inhibit a NAND gate and what is its output when inhibited? 

Logic 0 is the logic signal required to inhibit a NAND gate and 1 is its output, irrespective of all other inputs, when inhibited.

29. What is multiplexing?

Multiplexing is an operation performed with digital logic circuits several lines into single lines into a single line in a specified sequence.

30. What is an encoder?

An encoder is a logic circuit that produces coded binary inputs from encoded inputs.

31. What is a DE multiplexer?

DE multiplexer is a logic circuit that accepts one data input and distributes it over several outputs.it is also most important interview question of digital electronics.

32. What is a decoder?

Decoder is a logic circuit that decodes from binary to octal decimal, hexadecimal, or any other code such as 7-segment circuit etc.

33. What is sequential circuit?

Sequential logic circuit is that circuit in which outputs of the circuit remain in their state, until instructed to change it. In other words sequential logic circuit may be defined as that logic circuit whose outputs are determined by the sequence in which input signal are applied.

34. What is a flip-flop?

A flip-flop is a basic memory element that is made of an assembly of logic gates and is used to store 1-bit of information. Flip flop is main subject of digital electronics which are mostly asked in interview.

35. What is a latch?

It is a D-type of flip-flop and stores one bit of data.

36. What is an excitation table?

Excitation table gives information about what should be the flip-flop inputs if the outputs are specified before and after the clock pulses.

37. What is a state table?

State table consists of complete information about present state, next state, and out puts of a sequential circuit.

38. What is meant by a counter?

Counter is a digital circuit which is used to count pulses and give the output in the binary form.  These are also main interview question of digital electrics.

39. What is difference between synchronous and asynchronous counters?

In a synchronous counter all the flip-flops get clocked simultaneously where as in an asynchronous counter the output of one flip-flop drives another flip-flop.

40. What is a ripple counter?

When the output of one flip flop drives another flip flop, the counter is called a ripple counter.

Hence these are some digital electronics interview questions. If you have any query in theses question you must comment below in comment box.

If you want to more about digital electronics system you must watch this video.

Difference between CFL and LED bulbs

In this article will knwo about the difference between LED and CFL bulbs . CFL and LED both is a lamp which is use to produce bright light . but due shortege of energy resorces its compulsary to use less energy consumption equipment, as like LED and CFL.
Difference between CFL and LED bulbs, CFL Vs LED
LED is more costly and longer life than CFL,  it is also most compact than LED.
we will show you difference between CFL and LED bulbs.

Difference between CFL and LED Bulbs

1. LEDs, or Light Emitting Diodes, have been in public use a lot longer than Compact 
Fluorescent Lamps or CFLs. These are the tiny diodes that light up to indicate that something is on, or blink to attract attention.
2. It is much and more efficient
It is low efficient
3. Led is the over long term are cheaper
It is the over long term are costly
4.  LEDs are substantially smaller compared to CFL.
CFL are substantially longer compared to LED.
5. Its efficiency is very high in comparison of CFL bulbs.
Its efficiency is less in comparison of LED bulbs. Its efficiency is less.
6. The electrical power used is LED 6-8 watts. It is equal to 60 watts bulbs.
In case of CFL electrical power used is approx. 13-15 watts. Which is also equal to 60 watts bulbs?
7. The energy saving in LED up to an 80% a year in energy costs.
The energy saving in CFL up to an 75% a year in energy costs.
8. LED life is 50000 hours. Which is very useful for essential cost?
CFL life is 80000 hours. Which is greater than LED bulbs, it is basic difference between CFL and LED.
9. Its cost is very high as compare to CFL.
Its cost is less as compare to LED
10. LED is high durable compare than CFL
CFL is less durable than LED
it is basic difference between LED and CFL bulbs
11. Its size is small and less maintenance
Its size is high and maintenance cost high
12. In case LED its remains cool in long time
In case of CFL it gets heated quickly
LEDs do not need extra components, like the ballasts that CFLs need.

CFL need extra component but in case of led there is does not need extra component.

Hence it is basic difference between LED and CFL bulbs, if you will find any incorect in above article please comment below in comment box.

if you want to know more about the difference between CFL and LED bulbs, you must watch this video.

Primary distribution system, Secondary distribution system

in this article we will know about the primary distribution system, we will also studied about the main primary distribuiton system . we will also know about the secondary distribution system.

Primary distribution system

primary distribution system, types of primary distribution system
Primary distribution system is of four types-
1. Radial feeder
2. Parallel feeder
3. Loop feeder
4. Primary network

1. Radial feeder

Radial feeder system is main types of primary distribution system
This feeder is used to supply small and medium residential, commercial loads. It radiates from the secondary substation and branches into sub feeder and laterals which extended into all parts of service area. The feeder and sub feeder are three phase three wire circuit. The distribution transformer is connected to primary   feeder, sub feeder and laterals through fused cutouts.

2. Parallel feeder

It consists of duplicate feed system having two radial feeders running in parallel. Each feeder supplies about half of total load of the area but has a capability to supply the entire load in the event of an outage on the other feeder. Failure of any feeder will result interruption of service until the load normally supplied by the faulted feeder is transferred to the other feeder by automatic control switch.

3. Loop feeder

A system of two or more radial feeders originating from the same or secondary different substation and separately routed through load area is known as loop feeder.it is also main types of primary distribution system.
If ends of two feeders are tied together through normally open switching device the resulting arrangement is known as open loop system and if ends are tied together by means of normally closed switching device the result is a ring loop feeder.

4. Primary Network

This system consists of a number of interconnected feeders. Two or more secondary transmission circuit supply two or more secondary substations from which the feeder takes off. Because the feeder is interconnected power is supplied to all the distribution transformers even though a part of network may be out of service. Each secondary substation consists of a transformer and the necessary switch gear to isolate the faulty feeder and to control feeder.
Secondary distribution system
The secondary distribution system consist of three phase four wire 400V distributors laid along road sides. The service connection are tapped off the off the distributors at convenient points. These connection may be 1 phase two wire circuit or 3 phase 4 wire circuit.These are basic types of primary distribution system.

Secondary distribution system

The secondary system used are-

1. Radial
2. Open loop
3. Network distribution

1. Radial system

It takes off from the distribution transformer and runs through the area to be served by it.

2. Open loop system

This system consist of two distributors taking off from the same distribution transformer and running in different directions and supplying different areas at time of fault one of distributors, power can supplied through partially, from the other distributor.

3. Network distribution

A network grid system consist of a number of inter connected distributors. Two or more distribution transformers feed the distribution network and operate continuously in parallel. This system is suitable for serving high load density metropolitan areas. Which are shows in secondary distribution system.


 Hence these are primary distribution system. if you will find any incorect above article please comment below in comment box.