An insulator or dielectric could be conveniently defined as a material that does not conduct electricity, if not the fact all known materials conduct a measurable amount of electricity. Nevertheless, insulators are readily distinguished from conductors. At room temperature, the conductivity of a good insulator typically is more than 20 orders of magnitude smaller than that of a good conductor and the difference becomes larger at lower temperatures.
The physics that underlies the vast difference between the electrical conductivity of insulators and conductors is the first topic considered. The above things that discusses are devoted to properties of insulators, including the importance of the insulator-electrode contacts in determining conduction processes. This article concludes with a brief description of some of the ways an insulator loses its ability to insulate when electrically stressed to the point of breakdown.
Imagine that you are viewing a videos film about an Antarctic expedition on your computer. It would be ideal if you can see the recordings of the expedition, hear a commentary on the expedition at the same time and listen to the conversation of the members of the expedition on your computer. All this and more is possible using a CD-ROM as a storage medium. The CDs used in a CD-ROM are similar to audio CDs and can store vast quantities of data---700MB or more.
To read a CD-ROM you need an input device called the CD-ROM drive. A CD-ROM can not be erased or written onto without the help of a special device called the CD-Recorder.
CD-ROMs are used whenever large volume of data needs to be stored and distributed. Databases on medicine, tourism, literature etc are available on CD-ROM s. Encyclopedia and dictionaries are also available on CD-ROMs.
To read a CD-ROM you need an input device called the CD-ROM drive. A CD-ROM can not be erased or written onto without the help of a special device called the CD-Recorder.
CD-ROMs are used whenever large volume of data needs to be stored and distributed. Databases on medicine, tourism, literature etc are available on CD-ROM s. Encyclopedia and dictionaries are also available on CD-ROMs.
The USB drive is a portable, easy to use and secure solution for transporting and sharing your data. USB stands for Universal Serial Bus. Lightweight and compact , the USB drive is incredibly small and can fit right into your pocket, requires no cables, power supplies or batteries. It plugs into any computer’s USB port.
To make it work, plug the drive into a USB port on your computer. It is plug and play for new version of operating system, but some operating systems, such as windows 95/98 do not automatically load the driver.
A single USB port can be used to connect up to127 peripheral devices, such as mice, modems, and keyboards. There are various types of USB length of drive , storing from 8Mb to more then 1GB.
To make it work, plug the drive into a USB port on your computer. It is plug and play for new version of operating system, but some operating systems, such as windows 95/98 do not automatically load the driver.
A single USB port can be used to connect up to127 peripheral devices, such as mice, modems, and keyboards. There are various types of USB length of drive , storing from 8Mb to more then 1GB.
The original memory stick was available in sizes up to 128MB, and a sub-version, Memory Stick Select allowed two banks of 128 MB selectable by a slider switch, essentially two cards squeezed into one. The largest capacity Memory Sticks currently available is 32GB. According to Sony, the Memory Stick PRO has a maximum theoretical size of 2TB.[2]
As of January 2010[update], it appears that Sony is beginning to combine both formats in their products. All digital cameras and camcorders announced by Sony at the 2010 Consumer Electronics Show can use SD and SDHC cards as well as Memory Sticks.[3][4][5][6][7] Furthermore, Sony is releasing its own line of SD cards.[8] Many claim this development as the end of format war between Memory Stick and SD card. But Sony has not abandoned the format, in fact it will continue development of the format for the foreseeable future. A prime example is the development of WiFi transfers through a still in development, special Memory Stick Pro-Duo.
As of January 2010[update], it appears that Sony is beginning to combine both formats in their products. All digital cameras and camcorders announced by Sony at the 2010 Consumer Electronics Show can use SD and SDHC cards as well as Memory Sticks.[3][4][5][6][7] Furthermore, Sony is releasing its own line of SD cards.[8] Many claim this development as the end of format war between Memory Stick and SD card. But Sony has not abandoned the format, in fact it will continue development of the format for the foreseeable future. A prime example is the development of WiFi transfers through a still in development, special Memory Stick Pro-Duo.
Applications
Typically, Memory Sticks are used as storage media for a portable device, in a form that can easily be removed for access by a personal computer. For example, Sony digital compact cameras use Memory Sticks for storing image files. With a Memory Stick-capable Memory card reader a user can copy the pictures taken with the Sony digital camera to a computer. Sony typically includes Memory Stick reader hardware in its first party consumer electronics, such as digital cameras, digital music players, PDAs, cellular phones, the VAIO line of laptop computers, and the PlayStation Portable.
A special Memory Stick can be inserted in the hindquarters[16] of Sony's AIBO robot pet, to enable the use of Aiboware—software intended for use on AIBOs. The Sticks include a copy protection mechanism used by the robot, allowing users to write programs. These are referred to as programmable or programming. Only 8 MB and 16 MB versions are available.
A special Memory Stick can be inserted in the hindquarters[16] of Sony's AIBO robot pet, to enable the use of Aiboware—software intended for use on AIBOs. The Sticks include a copy protection mechanism used by the robot, allowing users to write programs. These are referred to as programmable or programming. Only 8 MB and 16 MB versions are available.
Provide a path for adapter peripheral device to the system bus. It is a set of standardized connector (Dolt) located on the system board, It means motherboard, which provide connecting to the data path, new peripherals devices such as modem, Monitor, printer etc. For system to newly develops component, there most board,this common bus/slot.It is an opening in a computer where a circuit board can be inserted to add new capabilities to the computer like upgrading the quantity of PC, graphic and connection to a local network. The daughter board inserted into the expansion slots are metallic (typical copper) spring figure that clamp into the expansion card,where it is inserted into the slots each of the figures matches up with one segment of the card edge connection of the slot and card combination.
On early PCI expansion cards were used to add some of the basic function of the system include memory serial port and even the clock and calendar function of the PC. Today PC still and some of the function through expansion cards, but many of this capabilities are now inbuilt into the motherboard. In modern PCS expansion card one use to improve or add to the capabilities of the system to add cards for special purpose hardware and connect to a network. Expansion card now allow a PC to have o capture, sound,fax,scanner and network capabilities.
On early PCI expansion cards were used to add some of the basic function of the system include memory serial port and even the clock and calendar function of the PC. Today PC still and some of the function through expansion cards, but many of this capabilities are now inbuilt into the motherboard. In modern PCS expansion card one use to improve or add to the capabilities of the system to add cards for special purpose hardware and connect to a network. Expansion card now allow a PC to have o capture, sound,fax,scanner and network capabilities.
Assume that an organization has bought a powerful computer to meet its growing needs. The problem now is to shift the massive databases ( e.g a collection of related files in which an employee database can contain employee code file, attendance file , loan file etc) from the old machines to the new ones. Using diskettes as the backup medium is cumbersome, as they cannot store large amounts of data. In such cases, a cartridge tape is a very convenient back up media as it can store many megabytes of data. There are various types of cartridges and lengths of tape that can store from 40 megabytes to 25 gigabytes of data. A cartridge tape is made of plastic coated with a magnetic material and is similar to a video cassette tape. The tape is divided into tracks which run along the entire length of the tape. Data is recorded along these tracks. Just as you need a disk drive to read or write data onto a disk, you need a cartridge tape drive, which in an input-output device for a cartridge tape.
Data on a cartridge tape is stored sequentially. Therefore, if you want to access data stored at the end of the tape, you will have to run through the entire tape till you come to the end. This is in direct contrast to accessing data on disks wherein data can be accessed randomly. A good analogy here is the audio tape or the gramophone record. If you want to listen to a song recorded in the middle of the tape, you have to forward the tape till you come to the point where the song stars where as in the gramophone record you can directly place the gramophone head on the required sound track. Cartridge tapes are used wherever the volume of data or software to be backup is very large.
Data on a cartridge tape is stored sequentially. Therefore, if you want to access data stored at the end of the tape, you will have to run through the entire tape till you come to the end. This is in direct contrast to accessing data on disks wherein data can be accessed randomly. A good analogy here is the audio tape or the gramophone record. If you want to listen to a song recorded in the middle of the tape, you have to forward the tape till you come to the point where the song stars where as in the gramophone record you can directly place the gramophone head on the required sound track. Cartridge tapes are used wherever the volume of data or software to be backup is very large.
Data needs to be stored for later use on storage media. If the volume of data that needs to be stored is small floppy disk are enough. However when the amount of data to be stored is huge, storage media with larger storage capacities are required.
The data Storage Devices come in many sizes and shapes. And more over the technology used for the storage of the data over them is also altogether different. The storage devices are one of the most important components of the computer system. The memory is of two types; one is the primary memory and the other one is the secondary memory.
The primary memory is the volatile memory and the secondary memory is the non volatile memory. The volatile memory is the kind of the memory that is erasable and the non volatile memory is the one where in the contents cannot be erased. Basically when we talk about the data storage devices it is generally assumed to be the secondary memory.
The secondary memory is used to store the data permanently in the computer. The secondary storage devices are usually as follows: hard disk drives – this is the most common type of storage device that is used in almost all the computer systems. The other ones include the floppy disk drives, the CD ROM, and the DVD ROM. The flash memory, the USB data card etc.
The storage devices are used to record the data over any storage surface. The memories may also be of different types depending upon the architecture and the design like the optical data storage memory, magnetic media storage and the mechanical storage media etc and also the flash memory devices etc.
The storage devices are actually defined as the peripheral unit which holds the data like the tape, disk, or flash memory card etc. The most of the drives that are used for the purpose of data storage are fragile and the data can be easily corrupted in them. The data storage devices are the ones that are also used for the backup and the archiving of the data. The data storage devices were at a time in the past used to be too costly and expensive. But these days the data storage devices are becoming cheap day by day. Hence the data storage devices price is falling. So, we are in a position to get a storage device for a comparatively cheaper price than the earlier drive. The technology is improving a lot and now the memory storage capacity has gone up TB.
The data in the storage devices can be in the form of the files, databases, digital video and the audio etc. The storage devices that are called as the non volatile can store the data permanently until otherwise erased purposely. This is in the case of the hard disk drives or the floppy disk drives.
The other kinds of the storage media like for example the CD and the DVD can even have again two types of the storage; the first one is that in which the data once written cannot be erased. It is stored permanently over it. While the second type of the CD’s or the DVD’s are called as the rewritable; where in the data that is once written can be erased completely and the same storage device can be used again for storing the different data.
The primary memory is the volatile memory and the secondary memory is the non volatile memory. The volatile memory is the kind of the memory that is erasable and the non volatile memory is the one where in the contents cannot be erased. Basically when we talk about the data storage devices it is generally assumed to be the secondary memory.
The secondary memory is used to store the data permanently in the computer. The secondary storage devices are usually as follows: hard disk drives – this is the most common type of storage device that is used in almost all the computer systems. The other ones include the floppy disk drives, the CD ROM, and the DVD ROM. The flash memory, the USB data card etc.
The storage devices are used to record the data over any storage surface. The memories may also be of different types depending upon the architecture and the design like the optical data storage memory, magnetic media storage and the mechanical storage media etc and also the flash memory devices etc.
The storage devices are actually defined as the peripheral unit which holds the data like the tape, disk, or flash memory card etc. The most of the drives that are used for the purpose of data storage are fragile and the data can be easily corrupted in them. The data storage devices are the ones that are also used for the backup and the archiving of the data. The data storage devices were at a time in the past used to be too costly and expensive. But these days the data storage devices are becoming cheap day by day. Hence the data storage devices price is falling. So, we are in a position to get a storage device for a comparatively cheaper price than the earlier drive. The technology is improving a lot and now the memory storage capacity has gone up TB.
The data in the storage devices can be in the form of the files, databases, digital video and the audio etc. The storage devices that are called as the non volatile can store the data permanently until otherwise erased purposely. This is in the case of the hard disk drives or the floppy disk drives.
The other kinds of the storage media like for example the CD and the DVD can even have again two types of the storage; the first one is that in which the data once written cannot be erased. It is stored permanently over it. While the second type of the CD’s or the DVD’s are called as the rewritable; where in the data that is once written can be erased completely and the same storage device can be used again for storing the different data.
Very often it might be required to create high quality visual on paper, which cannot be obtained using a printer. For this purpose, a plotter is used. A plotter is an output device that is used to create presentation visuals, charts, graphs, tables, diagrams.
A plotter consists of an arm that moves across the paper on which the diagram or graph needs to be drawn. A pen moves along the arm and itself moves relative to the paper. A combination of the two thus provides movement along the horizontal and vertical axes.
In some plotters, the paper is held stationary while the arm and the pens move over it. This is called a flat bed plotter. In the other type of plotter, the paper is wrapped around a drum and anchored at both ends. The drum rotates while the pen moves laterally along a fixed rail. This is called a drum plotter.
To draw clear and high quality diagrams a plotter needs high quality pens with special inks of different colors.
A plotter can be connected to a PC through the parallel port. A plotter is more software- dependent than any other peripheral and needs much more instructions than the printer for producing output.
Plotters are used in applications like CAD, which require high quality graphics on paper. Many of the plotters now available in the markets are desktop models that can be used with PCs. Business typically use plotters to present an analysis in visual terms (bar harts, graphs, diagrams etc) as well as for engineering drawings.
A plotter consists of an arm that moves across the paper on which the diagram or graph needs to be drawn. A pen moves along the arm and itself moves relative to the paper. A combination of the two thus provides movement along the horizontal and vertical axes.
In some plotters, the paper is held stationary while the arm and the pens move over it. This is called a flat bed plotter. In the other type of plotter, the paper is wrapped around a drum and anchored at both ends. The drum rotates while the pen moves laterally along a fixed rail. This is called a drum plotter.
To draw clear and high quality diagrams a plotter needs high quality pens with special inks of different colors.
A plotter can be connected to a PC through the parallel port. A plotter is more software- dependent than any other peripheral and needs much more instructions than the printer for producing output.
Plotters are used in applications like CAD, which require high quality graphics on paper. Many of the plotters now available in the markets are desktop models that can be used with PCs. Business typically use plotters to present an analysis in visual terms (bar harts, graphs, diagrams etc) as well as for engineering drawings.
Printers are output devices that print the result of an operation on paper. A printer is capable of producing output that contains printed words. It is also capable of printing straight lines and simple figures like squares, rectangles and circles. Printers are classified based on a number of parameters, like the mechanism used for printing, the speed of printing , the quality of output, the direction of printing and the kind of interface they have with the computer. The following section will elaborate on these parameters.
There are two main types of printers, impact printers and non-impact printers.
Impact printer
In impact printers, characters are printed by pressing a typeface against an inked ribbon, which makes a mark on the paper. The most commonly used impact printers is the Dot Matrix Printer.
In DMP, an arrangement of tiny hammers or pins strikes the ribbon to produce the desired characters. These tiny pins typically print in a matrix of 7 dots across and 9 dots down. The impact of the appropriate pins on paper through the inked ribbon forms letters made up of dots. A kind of printer with a vertical column of up to 48 small closely packed needles or pins each of which can be individually forced forward to press an ink ribbon against the paper. There are printers which use up to 24 vertical pins to print characters with a higher resolution. The speed is usually 30 to 550 cps( character per second).
DMPs are expensive but noisy. They can print both text and graphics. They can print any language without additional hardware. They can also be made to print in color by changing ribbons. These printers are used to produce internal reports and memos needed by organizations. The other types of impact printer are drum printers, daisy wheel printers, line printers, Braille printers. However, these printers are not as popular as DMPs.
Non-impact printer
In non-impact printers, there is no contact between the typeface and the paper while printing. They are much quicker than impact printer as their printing heads do not strike the paper.
The main type of non-impact printer are:
Laser printer: This printer use a light beam to form images on the paper using toner ink as the medium. The light beam strikes parts of a drum surface to form an image. Those parts of the drum surface, which are exposed to the light beam, become electrically charged. Only these electrically charged areas attract the toner ink particles. These toner particles are then deposited on, and permanently fixed to the paper using heat or pressure.
Ink jet printer: ink jet printer, invented by canon, use jets of ink to print characters on paper. Three color of cartridges which combine magenta, yellow and cyan inks are used to create color tones. A black cartridge is also used for crisp monochrome output. It produces high resolution dot matrix characters.
Thermal printer: Thermal printers use heat to print characters on paper. Mostly ink jets use thermal technology ,whereby heat is used to fire ink onto the paper. These printers are used in calculators and many fax machines. The drawback with this technology is that it produces low-quality and low resolution print.
There are two main types of printers, impact printers and non-impact printers.
Impact printer
In impact printers, characters are printed by pressing a typeface against an inked ribbon, which makes a mark on the paper. The most commonly used impact printers is the Dot Matrix Printer.
In DMP, an arrangement of tiny hammers or pins strikes the ribbon to produce the desired characters. These tiny pins typically print in a matrix of 7 dots across and 9 dots down. The impact of the appropriate pins on paper through the inked ribbon forms letters made up of dots. A kind of printer with a vertical column of up to 48 small closely packed needles or pins each of which can be individually forced forward to press an ink ribbon against the paper. There are printers which use up to 24 vertical pins to print characters with a higher resolution. The speed is usually 30 to 550 cps( character per second).
DMPs are expensive but noisy. They can print both text and graphics. They can print any language without additional hardware. They can also be made to print in color by changing ribbons. These printers are used to produce internal reports and memos needed by organizations. The other types of impact printer are drum printers, daisy wheel printers, line printers, Braille printers. However, these printers are not as popular as DMPs.
Non-impact printer
In non-impact printers, there is no contact between the typeface and the paper while printing. They are much quicker than impact printer as their printing heads do not strike the paper.
The main type of non-impact printer are:
Laser printer: This printer use a light beam to form images on the paper using toner ink as the medium. The light beam strikes parts of a drum surface to form an image. Those parts of the drum surface, which are exposed to the light beam, become electrically charged. Only these electrically charged areas attract the toner ink particles. These toner particles are then deposited on, and permanently fixed to the paper using heat or pressure.
Ink jet printer: ink jet printer, invented by canon, use jets of ink to print characters on paper. Three color of cartridges which combine magenta, yellow and cyan inks are used to create color tones. A black cartridge is also used for crisp monochrome output. It produces high resolution dot matrix characters.
Thermal printer: Thermal printers use heat to print characters on paper. Mostly ink jets use thermal technology ,whereby heat is used to fire ink onto the paper. These printers are used in calculators and many fax machines. The drawback with this technology is that it produces low-quality and low resolution print.
A light pen is a pointing device that can be used to select an option by simply pointing at it, or to draw figures directly on the screen.
Figure…….
A light pen has a photo-detector as its tip. This detector can detect changes in brightness of the screen. When the pen is pointed at a particular spot on the screen, it record change in brightness instantly and informs the computer about this. The computer can find out the exact spot with this information. Thus, the computer can identify where you are pointing on the screen.
Light pens are useful for menu-based applications. Instead of moving the mouse around or using a keyboard, the user can select an option by pointing at it.
A light pen is also useful for drawing graphics in programs, such as computer aided design(CAD). An engineer, architect or a fashion designer can draw directly on the screen with the pen. Using a keyboard and a light pen , the designer can select colors and line thickness, reduce or enlarge drawings and edit drawings.
Figure…….
A light pen has a photo-detector as its tip. This detector can detect changes in brightness of the screen. When the pen is pointed at a particular spot on the screen, it record change in brightness instantly and informs the computer about this. The computer can find out the exact spot with this information. Thus, the computer can identify where you are pointing on the screen.
Light pens are useful for menu-based applications. Instead of moving the mouse around or using a keyboard, the user can select an option by pointing at it.
A light pen is also useful for drawing graphics in programs, such as computer aided design(CAD). An engineer, architect or a fashion designer can draw directly on the screen with the pen. Using a keyboard and a light pen , the designer can select colors and line thickness, reduce or enlarge drawings and edit drawings.
A light pen is a pointing device that can be used to select an option by simply pointing at it, or to draw figures directly on the screen.
Figure…….
A light pen has a photo-detector as its tip. This detector can detect changes in brightness of the screen. When the pen is pointed at a particular spot on the screen, it record change in brightness instantly and informs the computer about this. The computer can find out the exact spot with this information. Thus, the computer can identify where you are pointing on the screen.
Light pens are useful for menu-based applications. Instead of moving the mouse around or using a keyboard, the user can select an option by pointing at it.
A light pen is also useful for drawing graphics in programs, such as computer aided design(CAD). An engineer, architect or a fashion designer can draw directly on the screen with the pen. Using a keyboard and a light pen , the designer can select colors and line thickness, reduce or enlarge drawings and edit drawings.
Figure…….
A light pen has a photo-detector as its tip. This detector can detect changes in brightness of the screen. When the pen is pointed at a particular spot on the screen, it record change in brightness instantly and informs the computer about this. The computer can find out the exact spot with this information. Thus, the computer can identify where you are pointing on the screen.
Light pens are useful for menu-based applications. Instead of moving the mouse around or using a keyboard, the user can select an option by pointing at it.
A light pen is also useful for drawing graphics in programs, such as computer aided design(CAD). An engineer, architect or a fashion designer can draw directly on the screen with the pen. Using a keyboard and a light pen , the designer can select colors and line thickness, reduce or enlarge drawings and edit drawings.
Imagine a cardiac surgeon performing an intricate bypass surgery. In between, the surgeon needs to check the laboratory test results of the patient. Assuming that the information is stored on a computer, the surgeon can access the information through a keyboard, or better still, through a mouse. But how much more convenient it would be if the surgeon could only touch the screen on the option that is required to display the information. A touch screen input interface does exactly this. Touch screens are normally used when information has to be accessed with minimum effort.
Figure………
Touch screens are used in information-providing systems like the one explained above. It is also used in airline and railway reservation counters. The users indicate their current location and the destination by touching the screen and all the possible routes with timings and rates are displayed. These interfaces are also used in travel agencies to display the names and address of all hotels and other places of interest , at a desired destination. Touch screens are also used in stock exchanges.
Types of touch screens:
Resistive touch screens: The resistive touch screen is made sensitive to touch and the exact position is detected. This technology is recommended for use in point of sale, such as hotels and retail stores. This type of touch screens are generally the most affordable.
Infrared touch screens: The infrared touch screens is lined with light emitting devices and photo-detectors. When the user’s finger approaches the screen, the light beam is broken and is detected by the photo-detectors. The drawback with this technology is that your screen may sometimes react before you physically touch it.
Surface Acoustic touch screens: The surface acoustic wave technology is one of the most advanced touch screen. These screens send sound waves across your screen surface to look for interruptions caused by touch. Mostly it used for public information kiosks, computer based training or other high traffic indoor environments.
Capacitive touch screen: The capacitive touch screen is coated with a material that stores electrical charges. When the screen is touched, the charge is drawn to the point of contact. This charge is detected and measured by the circuits located at each corner of the screen. The circuits send the information to the controller for processing. Grease, water and dirt do not affect the capacitive touch screens.
Figure………
Touch screens are used in information-providing systems like the one explained above. It is also used in airline and railway reservation counters. The users indicate their current location and the destination by touching the screen and all the possible routes with timings and rates are displayed. These interfaces are also used in travel agencies to display the names and address of all hotels and other places of interest , at a desired destination. Touch screens are also used in stock exchanges.
Types of touch screens:
Resistive touch screens: The resistive touch screen is made sensitive to touch and the exact position is detected. This technology is recommended for use in point of sale, such as hotels and retail stores. This type of touch screens are generally the most affordable.
Infrared touch screens: The infrared touch screens is lined with light emitting devices and photo-detectors. When the user’s finger approaches the screen, the light beam is broken and is detected by the photo-detectors. The drawback with this technology is that your screen may sometimes react before you physically touch it.
Surface Acoustic touch screens: The surface acoustic wave technology is one of the most advanced touch screen. These screens send sound waves across your screen surface to look for interruptions caused by touch. Mostly it used for public information kiosks, computer based training or other high traffic indoor environments.
Capacitive touch screen: The capacitive touch screen is coated with a material that stores electrical charges. When the screen is touched, the charge is drawn to the point of contact. This charge is detected and measured by the circuits located at each corner of the screen. The circuits send the information to the controller for processing. Grease, water and dirt do not affect the capacitive touch screens.
Another input device that is being increasingly used is the scanner. Often, there are situations when some information is available on paper is needed on the computer disk for further editing. The simplest way would be to take a photograph of the image directly from the source, and convert it into a form that can be saved on the disk and then printed.
A scanner scans an image and transforms the image to ASCII code that is used by a computer to represent the characters you find on your keyboard, such as , alphabets, numbers, punctuation marks and graphics. These can be edited, manipulated and printed.
Type of scanners:
Flatbed scanner: The flatbed scanner is most common desktop scanner. It resembles the copy machine. In the flatbed scanner, the item being scanned resets on a glass plate while the scanning head moves underneath it. It works like a copy machine except that it creates a file of the document rather than a paper copy.
Sheetfed scanner: Personal sheetfed scanner have gained popularity during last few years. These devices are more like a fax machines, because they move the page being scanned past the scanning head, rather than the other way around. The main difference to flatbed scanners is that the image sensor does not move but the document itself is pulled past the mounted image sensor.
Handheld scanner: The handheld scanner is a scanning device where the scanning element is built into a small handheld unit. The handheld unit is then waved or rolled over the item being scanned.
Many scanners are available now a days that are capable of not only scanning text and graphics, but also integrating text and graphics files.
Scanners are used to reproduce photographs on the computer screen. They can be used in training program using computers and in desktop publishing. Businesses use scanners for storing documents on the computer.
A scanner scans an image and transforms the image to ASCII code that is used by a computer to represent the characters you find on your keyboard, such as , alphabets, numbers, punctuation marks and graphics. These can be edited, manipulated and printed.
Type of scanners:
Flatbed scanner: The flatbed scanner is most common desktop scanner. It resembles the copy machine. In the flatbed scanner, the item being scanned resets on a glass plate while the scanning head moves underneath it. It works like a copy machine except that it creates a file of the document rather than a paper copy.
Sheetfed scanner: Personal sheetfed scanner have gained popularity during last few years. These devices are more like a fax machines, because they move the page being scanned past the scanning head, rather than the other way around. The main difference to flatbed scanners is that the image sensor does not move but the document itself is pulled past the mounted image sensor.
Handheld scanner: The handheld scanner is a scanning device where the scanning element is built into a small handheld unit. The handheld unit is then waved or rolled over the item being scanned.
Many scanners are available now a days that are capable of not only scanning text and graphics, but also integrating text and graphics files.
Scanners are used to reproduce photographs on the computer screen. They can be used in training program using computers and in desktop publishing. Businesses use scanners for storing documents on the computer.
Another input device that is being increasingly used is the scanner. Often, there are situations when some information is available on paper is needed on the computer disk for further editing. The simplest way would be to take a photograph of the image directly from the source, and convert it into a form that can be saved on the disk and then printed.
A scanner scans an image and transforms the image to ASCII code that is used by a computer to represent the characters you find on your keyboard, such as , alphabets, numbers, punctuation marks and graphics. These can be edited, manipulated and printed.
Type of scanners:
Flatbed scanner: The flatbed scanner is most common desktop scanner. It resembles the copy machine. In the flatbed scanner, the item being scanned resets on a glass plate while the scanning head moves underneath it. It works like a copy machine except that it creates a file of the document rather than a paper copy.
Sheet fed scanner: Personal sheet fed scanner have gained popularity during last few years. These devices are more like a fax machines, because they move the page being scanned past the scanning head, rather than the other way around. The main difference to flatbed scanners is that the image sensor does not move but the document itself is pulled past the mounted image sensor.
Hand held scanner: The hand held scanner is a scanning device where the scanning element is built into a small hand held unit. The hand held unit is then waved or rolled over the item being scanned.
Many scanners are available now a days that are capable of not only scanning text and graphics, but also integrating text and graphics files.
Scanners are used to reproduce photographs on the computer screen. They can be used in training program using computers and in desktop publishing. Businesses use scanners for storing documents on the computer.
A scanner scans an image and transforms the image to ASCII code that is used by a computer to represent the characters you find on your keyboard, such as , alphabets, numbers, punctuation marks and graphics. These can be edited, manipulated and printed.
Type of scanners:
Flatbed scanner: The flatbed scanner is most common desktop scanner. It resembles the copy machine. In the flatbed scanner, the item being scanned resets on a glass plate while the scanning head moves underneath it. It works like a copy machine except that it creates a file of the document rather than a paper copy.
Sheet fed scanner: Personal sheet fed scanner have gained popularity during last few years. These devices are more like a fax machines, because they move the page being scanned past the scanning head, rather than the other way around. The main difference to flatbed scanners is that the image sensor does not move but the document itself is pulled past the mounted image sensor.
Hand held scanner: The hand held scanner is a scanning device where the scanning element is built into a small hand held unit. The hand held unit is then waved or rolled over the item being scanned.
Many scanners are available now a days that are capable of not only scanning text and graphics, but also integrating text and graphics files.
Scanners are used to reproduce photographs on the computer screen. They can be used in training program using computers and in desktop publishing. Businesses use scanners for storing documents on the computer.
A mouse was invented by Douglas Engelbart of Stanford Research Center in 1963, and pioneered by Xerox in the 1970s.
A mouse is an input device that is important for graphical user interfaces because user can simply point to options and click a mouse button. These types of applications are often called point-and –click programs. The mouse is also important for graphics programs that allow user to draw pictures by using the mouse like a pen, pencil or paintbrush.
A mouse may have one, two or three buttons. The function of each button is determined by the program that uses the mouse. A software package may use one, two or all three of them. In its simplest form, a mouse has one button. Moving the mouse on a flat surface produces a corresponding movement of a pointer on the screen. Placing the pointer on an option and clicking the button results in selecting that option.
A mouse may be classified as a mechanical mouse or an optical mouse, on the basis of the technology it uses. In a mechanical mouse, the ball that projects through the bottom surface rotates as the mouse is moved along a flat surface. The direction of rotation is detected and relayed to the computer by the switches inside the mouse. Microsoft, IBM are some well known makers of the mechanical mouse.
An optical mouse uses a light beam instead of a rotating ball to detect movements across a specially patterned mouse pad. MSC corporation makes the optical mouse that uses LEDs and photo-detectors to trap movement.
Some categories of mouse are listed below:
Trackball mouse: In a trackball mouse , the ball is rolled at one place with the thumb, fingers and palms rather than rolling the mouse on the table top.
Joystick mouse: A joystick usually includes two upright sticks which are moved with the hand and a button is pressed on either stick. Joystick mouse is basically used by children, recreational users and other users who prefer the joystick over the mouse or trackball.
Light pen mouse: A light pen utilizes a light sensitive detector, requiring you to hold a pen and point it at the screen.
Wireless mouse: The wireless mouse is a mouse without a cable. This mouse works up to one and a half meters away from the computer.
Touch pad mouse: A touch pad is a small, flat , rectangular pointing device that is sensitive to pressure and motion. The devices are mostly used on portable computers.
A mouse is an input device that is important for graphical user interfaces because user can simply point to options and click a mouse button. These types of applications are often called point-and –click programs. The mouse is also important for graphics programs that allow user to draw pictures by using the mouse like a pen, pencil or paintbrush.
A mouse may have one, two or three buttons. The function of each button is determined by the program that uses the mouse. A software package may use one, two or all three of them. In its simplest form, a mouse has one button. Moving the mouse on a flat surface produces a corresponding movement of a pointer on the screen. Placing the pointer on an option and clicking the button results in selecting that option.
A mouse may be classified as a mechanical mouse or an optical mouse, on the basis of the technology it uses. In a mechanical mouse, the ball that projects through the bottom surface rotates as the mouse is moved along a flat surface. The direction of rotation is detected and relayed to the computer by the switches inside the mouse. Microsoft, IBM are some well known makers of the mechanical mouse.
An optical mouse uses a light beam instead of a rotating ball to detect movements across a specially patterned mouse pad. MSC corporation makes the optical mouse that uses LEDs and photo-detectors to trap movement.
Some categories of mouse are listed below:
Trackball mouse: In a trackball mouse , the ball is rolled at one place with the thumb, fingers and palms rather than rolling the mouse on the table top.
Joystick mouse: A joystick usually includes two upright sticks which are moved with the hand and a button is pressed on either stick. Joystick mouse is basically used by children, recreational users and other users who prefer the joystick over the mouse or trackball.
Light pen mouse: A light pen utilizes a light sensitive detector, requiring you to hold a pen and point it at the screen.
Wireless mouse: The wireless mouse is a mouse without a cable. This mouse works up to one and a half meters away from the computer.
Touch pad mouse: A touch pad is a small, flat , rectangular pointing device that is sensitive to pressure and motion. The devices are mostly used on portable computers.
A computer uses its software to store, process and retrieve information. Computer software can be divided into two types:
1. Application software
2. System software
Application software refers to the software that enables users to perform specific tasks for example, MS-Word is used to create and edit a document.
System software refers to the software that enables a computer to function for eg; windows operating system is system software. The operating system provides a consistent environment for other software to execute commands.
A user can give the computer instructions through input devi9ces such as mouse or keyboard to the operating system. Some of these commands are built into the operating systems, while others are issued through the use of application. The operating system becomes the center through which the system hardware, other software and the user communicate. The rest of the components of the system work together through the operating system.
Function of OS
The various tasks that an operating system performs are:
Process management:
A process is an instance of a program running in a computer. Many processes can run simultaneously in a computer. The OS manages all the process and ensures error-free output. For example, while typing a letter you might like to listen to music on the computer.
I/O operations
The operating system provides a user with an I/O devices so that the user can enter data and access the output. If an I/O device is being used by one process and other processes request for it, the OS schedules the allocation of the device to the second process.
File management
The OS enables you to perform file operation such as creating a file, naming it, opening it, reading it, writing in it and closing it.
Memory management
The OS keeps tracks of the part of the memory that is in use and the part that is free. It then allocates the free part of the memory to other processes ensuring that memory is fully utilized.
1. Application software
2. System software
Application software refers to the software that enables users to perform specific tasks for example, MS-Word is used to create and edit a document.
System software refers to the software that enables a computer to function for eg; windows operating system is system software. The operating system provides a consistent environment for other software to execute commands.
A user can give the computer instructions through input devi9ces such as mouse or keyboard to the operating system. Some of these commands are built into the operating systems, while others are issued through the use of application. The operating system becomes the center through which the system hardware, other software and the user communicate. The rest of the components of the system work together through the operating system.
Function of OS
The various tasks that an operating system performs are:
Process management:
A process is an instance of a program running in a computer. Many processes can run simultaneously in a computer. The OS manages all the process and ensures error-free output. For example, while typing a letter you might like to listen to music on the computer.
I/O operations
The operating system provides a user with an I/O devices so that the user can enter data and access the output. If an I/O device is being used by one process and other processes request for it, the OS schedules the allocation of the device to the second process.
File management
The OS enables you to perform file operation such as creating a file, naming it, opening it, reading it, writing in it and closing it.
Memory management
The OS keeps tracks of the part of the memory that is in use and the part that is free. It then allocates the free part of the memory to other processes ensuring that memory is fully utilized.
Blue-tooth is a wireless protocol that is used to communicate from one device to another in a small area usually less than 30 feet. It is a wireless, which is at lost-cost radio solution that enables small devices such as PDAs, cell phones and palmtops to communicate between each other and with the internet. The technology will also be extended to the desktop so that printers or scanners can communicate with desktop computers at short distance without wires, thereby enhancing ease of use and reducing wiring problems.
The original developers of the Blue-tooth technology were Ericsson, Intel, Microsoft, IBM, Nokia corporation and Toshiba. The technology enables data connection between electronic devices such as desktop computers, wireless phones, electronic organizers and printers in the 2.4 GHz range. Blue-tooth depends on mobile devices equipped with a chip for sending and receiving information.
This technology is a specification designed to enable wireless communication between small mobile devices. The original idea behind the technology was the concept to eliminate the need for proprietary cables, which are currently required to enable device connectivity. A typical e.g would be connecting a digital camera to a PC without cables. Blue-tooth is a standard for a small cheap radio chip to be plugged into computers, printers, mobile phones etc.
The features of Blue-tooth wireless technology are wireless headsets, mobile phones, mobile PCs, plug in cards, hand held PCs, wireless printing, automotive(including wireless headsets and door lock/unlock features, consume electronics(cameras, VCRs, Walkman), access points , electronics pens, mobile music players, entertainment robots
The original developers of the Blue-tooth technology were Ericsson, Intel, Microsoft, IBM, Nokia corporation and Toshiba. The technology enables data connection between electronic devices such as desktop computers, wireless phones, electronic organizers and printers in the 2.4 GHz range. Blue-tooth depends on mobile devices equipped with a chip for sending and receiving information.
This technology is a specification designed to enable wireless communication between small mobile devices. The original idea behind the technology was the concept to eliminate the need for proprietary cables, which are currently required to enable device connectivity. A typical e.g would be connecting a digital camera to a PC without cables. Blue-tooth is a standard for a small cheap radio chip to be plugged into computers, printers, mobile phones etc.
The features of Blue-tooth wireless technology are wireless headsets, mobile phones, mobile PCs, plug in cards, hand held PCs, wireless printing, automotive(including wireless headsets and door lock/unlock features, consume electronics(cameras, VCRs, Walkman), access points , electronics pens, mobile music players, entertainment robots
For win NT
First of all enter into the Bios setting by pressing F2 or Del or F12 keys form the keyboard.
Enter into the configuration and make CD-ROM as first boot device and harddisk as second boot device.
Save and exit the Bios by pressing the key F10 and “y”
After that put an O/S into your CD-ROM and the computer restarts automatically.
After computers restarts press any key when 5 dots appears.
You will see the manage windows XP professional setup”, welcome to setup”.
Wait a few minutes and again you will find a new message that is welcome to setup
This partition of the setup programs prepares Microsoft windows XP to run as your computer.
To setup windows XP now press Enter.
· To repair a windows XP instructions using recovery consol press “R”.
· To quit setup without installing windows XP press F3.
.
This time you have to press enter key.
After pressing enter key wait for sometime.
Following message will appear in your computer and this time you have to press F8 to agree license agreement.
F8 = I agree Esc = I don’t agree page down = next page
After license agreement you will again see another message.
F3 = quit
R = Repair
Esc = Don’t repair
In this period of time if you want to repair then press “R” to repair. If one of the following windows XP installation is damage, other wise press Esc key to escape from that page.
After choose any drive in which you want to put your operating system, but the computer will choose automatically the “C” drive.
Choose any-file system after you choose the drive.
For to format you have press ”F” or for to delete the drive you have to press “D” or “L”
After wait for sometime when setup copies file or wait until it reaches 0 to 100%.
Again wait for some time when it reaches 0 to 100%.
Computer will restarts automatically when it completed 100% to copy and again 5 dots appear but you should not press any key this time. If you press any key this time the setup will restarts again.
Booting will occur after restarts and you will find the message 39 minutes remaining. Now you have to wait and the time will decrease one by one at a time. In this mean time you have to put CD key and should correct the current date and time of the system as well as should choose the language or computer name too.
Wait until the time reaches 1 minute……it restarts automatically.
Install monitor settings and display settings after computer restarts.
Install VGA and sound from the motherboard.
Format is complete now your computer is ready to use.
First of all enter into the Bios setting by pressing F2 or Del or F12 keys form the keyboard.
Enter into the configuration and make CD-ROM as first boot device and harddisk as second boot device.
Save and exit the Bios by pressing the key F10 and “y”
After that put an O/S into your CD-ROM and the computer restarts automatically.
After computers restarts press any key when 5 dots appears.
You will see the manage windows XP professional setup”, welcome to setup”.
Wait a few minutes and again you will find a new message that is welcome to setup
This partition of the setup programs prepares Microsoft windows XP to run as your computer.
To setup windows XP now press Enter.
· To repair a windows XP instructions using recovery consol press “R”.
· To quit setup without installing windows XP press F3.
.
This time you have to press enter key.
After pressing enter key wait for sometime.
Following message will appear in your computer and this time you have to press F8 to agree license agreement.
F8 = I agree Esc = I don’t agree page down = next page
After license agreement you will again see another message.
F3 = quit
R = Repair
Esc = Don’t repair
In this period of time if you want to repair then press “R” to repair. If one of the following windows XP installation is damage, other wise press Esc key to escape from that page.
After choose any drive in which you want to put your operating system, but the computer will choose automatically the “C” drive.
Choose any-file system after you choose the drive.
For to format you have press ”F” or for to delete the drive you have to press “D” or “L”
After wait for sometime when setup copies file or wait until it reaches 0 to 100%.
Again wait for some time when it reaches 0 to 100%.
Computer will restarts automatically when it completed 100% to copy and again 5 dots appear but you should not press any key this time. If you press any key this time the setup will restarts again.
Booting will occur after restarts and you will find the message 39 minutes remaining. Now you have to wait and the time will decrease one by one at a time. In this mean time you have to put CD key and should correct the current date and time of the system as well as should choose the language or computer name too.
Wait until the time reaches 1 minute……it restarts automatically.
Install monitor settings and display settings after computer restarts.
Install VGA and sound from the motherboard.
Format is complete now your computer is ready to use.
The personal computer is although the most popular computer system, there are other computer systems too which is categorized on the basis of cost size and performance.
Personal computer or microcomputers:
Microcomputers is also known as personal computer. Most popular form of the computer in use today is probably the PC. The PC can be used for various applications and in fact, there are millions of PC already in use by individuals and organizations. The size of microcomputer is reduced to small pocket, calculator, laptop and network. It can communicate with different computer by using modem or LAN card. It can perform a diverse range of functions, from keeping track of household accounts to keeping records of the stores of a large manufacturing company. The most widespread is the IBM PC, based on microprocessors from Intel corporation, PS/2 and Apple’s Macintosh.
Minicomputers
It is medium in size which means it is bigger than microcomputer and smaller than mainframe. It can vary in size form a small desktop model to the size of a small filing cabinet. It resembles mainframe computers but they are comparatively small and less expensive. While most PCs are oriented towards single users. Mini systems are usually designed to simultaneously handle the needs of multiple users i.e more than one person use a mini computer at the same time. Today's computer vendors include IBM,Digital/Compaq and Hewlett Packard. IBM’s As/400 has probably been the most popular minicomputer of all time.
Mainframe computer
A mainframe is another form of a computer system that is generally more powerful than a typical mini system. Mainframes themselves may vary widely in cost and capability. They are used in large organizations for large scale jobs. It has faster processing unit, large storage capacity than typical mini computer. Currently IBM mainframe are dominant in the market with Hitachi, Amdahl and Fujitsu also producing machines. Prices start at several hundred thousand dollars.
Super computer
These systems are the largest fastest an the most expensive computer in the world. They are even faster than the mainframe(i.e 200 times faster). They are designed to process complex scientific jobs , bio-medical research, weather forecasting chemical analysis in laboratory and defense applications NEC’s earth simulator in JAPAN is how the worlds faster super computer.
Personal computer or microcomputers:
Microcomputers is also known as personal computer. Most popular form of the computer in use today is probably the PC. The PC can be used for various applications and in fact, there are millions of PC already in use by individuals and organizations. The size of microcomputer is reduced to small pocket, calculator, laptop and network. It can communicate with different computer by using modem or LAN card. It can perform a diverse range of functions, from keeping track of household accounts to keeping records of the stores of a large manufacturing company. The most widespread is the IBM PC, based on microprocessors from Intel corporation, PS/2 and Apple’s Macintosh.
Minicomputers
It is medium in size which means it is bigger than microcomputer and smaller than mainframe. It can vary in size form a small desktop model to the size of a small filing cabinet. It resembles mainframe computers but they are comparatively small and less expensive. While most PCs are oriented towards single users. Mini systems are usually designed to simultaneously handle the needs of multiple users i.e more than one person use a mini computer at the same time. Today's computer vendors include IBM,Digital/Compaq and Hewlett Packard. IBM’s As/400 has probably been the most popular minicomputer of all time.
Mainframe computer
A mainframe is another form of a computer system that is generally more powerful than a typical mini system. Mainframes themselves may vary widely in cost and capability. They are used in large organizations for large scale jobs. It has faster processing unit, large storage capacity than typical mini computer. Currently IBM mainframe are dominant in the market with Hitachi, Amdahl and Fujitsu also producing machines. Prices start at several hundred thousand dollars.
Super computer
These systems are the largest fastest an the most expensive computer in the world. They are even faster than the mainframe(i.e 200 times faster). They are designed to process complex scientific jobs , bio-medical research, weather forecasting chemical analysis in laboratory and defense applications NEC’s earth simulator in JAPAN is how the worlds faster super computer.
While it would not be wrong to say that the evolution of the computer began with the man’s need to count. The actual growth of this field happened in a short span of thirty years. This rapid development was characterized by phase of growth, which have to be called computer generations. Major technological developments in each generation led to smaller, cheaper, more powerful and efficient and reliable computers. Depending on device technology, system architecture, processing mode and languages used the computers are categorized into the following generations.
First generation (1940-1956)
The first generation computers used vacuum tubes. It is very huge in size and expensive. The examples of first generation computing devices are UNIVAC and ENIAC. The UNIVAC was the first commercial computer delivered to a business client, the U.S census Bureau in 1951.
Second generation(1956-1963)
It used transistors. In a span of ten years, transistors that were more efficient and cheaper replaced vacuum tubes.
Third generation (1964-1971)
It used integrated circuits(IC). In the early sixties, a major breakthrough was achieved when hundreds of transistors could be replaced on a single silicon chip. This integrated circuit(IC) became the basis of the third generation.
Fourth generation (1971-present)
It uses microprocessor. With the introduction of VLSI(very large scale integration) IC was replaced by it.
In 1981 IBM introduced its first computer for the home uses and in 1984 Apple introduced the Macintosh. Fourth generation computers also saw the development of graphical user interfaces(GUI), the mouse and hand held devices.
Fifth generation (present and beyond)
Artificial intelligence. This generation tries to infuse intelligence into computers. The development of those computers is still in its infancy but examples can be cited of various recognition system and robots.
First generation (1940-1956)
The first generation computers used vacuum tubes. It is very huge in size and expensive. The examples of first generation computing devices are UNIVAC and ENIAC. The UNIVAC was the first commercial computer delivered to a business client, the U.S census Bureau in 1951.
Second generation(1956-1963)
It used transistors. In a span of ten years, transistors that were more efficient and cheaper replaced vacuum tubes.
Third generation (1964-1971)
It used integrated circuits(IC). In the early sixties, a major breakthrough was achieved when hundreds of transistors could be replaced on a single silicon chip. This integrated circuit(IC) became the basis of the third generation.
Fourth generation (1971-present)
It uses microprocessor. With the introduction of VLSI(very large scale integration) IC was replaced by it.
In 1981 IBM introduced its first computer for the home uses and in 1984 Apple introduced the Macintosh. Fourth generation computers also saw the development of graphical user interfaces(GUI), the mouse and hand held devices.
Fifth generation (present and beyond)
Artificial intelligence. This generation tries to infuse intelligence into computers. The development of those computers is still in its infancy but examples can be cited of various recognition system and robots.
The BIOS performs a power on self-test, when the system is turn on. This test is used to ensure that the system is functioning properly and to gather information about that the system contains when a problem is identified with the system during power on-sl-test. The BIOS normally shows an error message. However,in some cases the problem is detected so early in the test that the BIOS cannot even access the video card to print the message, in this case the BIOS will produce a beeping pattern on the speaker to tell about a problem. The exact meaning of the beep codes depends on the type and version of BIOS that you have depending on the BIOS that you are using some BIOS use very simply beep codes in a pattern of verifying number of short beeps. While other may max short and long beeps. However,if you are using a PC made by a company that writes it's own BIOS, you will have to consult your owner's manual or the company's web site or other technical information for assistance. The three most popular type of BIOS are those made by American mega trend's INC, AMI, Award, Phoenix. The Phoenix Bios is famous for it's complicated beep patterns that are actually in up to four groups one or more beeps and then a pause, followed by a many as three more patterns.
Computer is an electronic device which can accept the data from user through input device and hold it for sometime to process the data and show to result in a output device.
Virus
(1) Worm virus (which attached with software)
(2) Boot Sector Virus
(3) Micro Virus
(4) Scripted Virus
Some dangerous programmer virus are as follows:
(1) Melisa
(2) DB M
(3) I Love You
(4) I raj on Horse
(5) Happy 99
(6) Nuclear
(7) Concept
Symptoms of Virus Infections:
- F1 to F12-Function key
- A to Z-Alphabet key
- Lab Enter Alt.etc-Operating key
- @,#,!,$,%,^,&,etc-Symbol key
- 0 to 9-Numerical key
- Alt65Alt90-A to Z
- Alt95Alt22-a to z
- Alt2 to Alt20-symbol
Virus
(1) Worm virus (which attached with software)
(2) Boot Sector Virus
(3) Micro Virus
(4) Scripted Virus
Some dangerous programmer virus are as follows:
(1) Melisa
(2) DB M
(3) I Love You
(4) I raj on Horse
(5) Happy 99
(6) Nuclear
(7) Concept
Symptoms of Virus Infections:
- Programs loading and execution take unusually long times.
- Changes in files and programs size color.
- Memory and disk spaces are suddenly reduced.
- Files disappear and strange files may process.
- Programs may fail to occur.
- Computer reboots in the middle of the process.
- Computer hangs on.
- Disk drives lit on unusually.
The voltage induced in secondary winding of transformer either in phase arrangement or a position comparison with primary voltages how the output terminal are consider when the terminal have been (DO).For high voltages and (c,d,a) for low voltage when the voltage induced between d and q in phase with voltage induced between d and q in phase with voltage induced the polarity is said to be subtractive otherwise polarity is addition.
When two corresponding terminals (Dand q) have been interconnected a suitable voltage is connected to one of the winding DO and the voltage assured between other two terminal.Q and q if the voltage connected between the terminals DO. The polarity is subtractive otherwise it is additive.
When two corresponding terminals (Dand q) have been interconnected a suitable voltage is connected to one of the winding DO and the voltage assured between other two terminal.Q and q if the voltage connected between the terminals DO. The polarity is subtractive otherwise it is additive.
The short circuit test consists in measuring the input characteristics (quantities) of the transformer when the secondary side is shorted and the primary side is supplied with a suitable decreased voltage so that the current in the winding are equal to related current.The purpose of the test is to determined:
(1)The value of copper loss in the winding
(2)The value of short circuit voltage (Vsc) ,resistance (Ro1) and reactance (Xo1).
The instruments are arranged as for the circuit diagram and small voltage about 10% of the rotted value is supplied to primary side keeping the secondary side short circuited.Voltage is gradually increased till rotted current flow in winding which is recorded by ammeter.This value of voltage whose cause to flow rotted current in short circuited condition is called short circuited voltage (Vsc).
Watt meter reading gives the value of 'Cu' loss.Iron in this case is very much negligible (But value is same as in no-load) then Cu loss.Copper loss depend on current similarly iron loss depend on voltage therefore copper loss is negligible in no-load and iron loss is neglible in short circuit condition.
(1)The value of copper loss in the winding
(2)The value of short circuit voltage (Vsc) ,resistance (Ro1) and reactance (Xo1).
The instruments are arranged as for the circuit diagram and small voltage about 10% of the rotted value is supplied to primary side keeping the secondary side short circuited.Voltage is gradually increased till rotted current flow in winding which is recorded by ammeter.This value of voltage whose cause to flow rotted current in short circuited condition is called short circuited voltage (Vsc).
Watt meter reading gives the value of 'Cu' loss.Iron in this case is very much negligible (But value is same as in no-load) then Cu loss.Copper loss depend on current similarly iron loss depend on voltage therefore copper loss is negligible in no-load and iron loss is neglible in short circuit condition.
When a test is performed by leaving one winding open and giving supply to the another side,the test on the transformer is performed to ensure the working condition to the transformer.The main of the open circuit test are as follows:
(a)To find no-load current (Io)
(b)To obtain no-load parameters i.e,IuIwRo1Xo
(c)To find core loss (V1Iocos)
Supply is given to low voltage side of the transformer because it is either to use lower rating equipment for the measurement.Supply is given through auto transformer to get variable voltage and also for matching winding voltage capacity.Supply voltage V1 is indicated by voltmeter,no load current.Io is measured by ammeter and core loss is given by watt meter.Secondary side was no current hence there is no copper (Cu) loss and primary side has small amount of no load current hence small copper loss is there which can be ignored.In this way,open circuit test is carried out in the transformer.
(a)To find no-load current (Io)
(b)To obtain no-load parameters i.e,IuIwRo1Xo
(c)To find core loss (V1Iocos)
Supply is given to low voltage side of the transformer because it is either to use lower rating equipment for the measurement.Supply is given through auto transformer to get variable voltage and also for matching winding voltage capacity.Supply voltage V1 is indicated by voltmeter,no load current.Io is measured by ammeter and core loss is given by watt meter.Secondary side was no current hence there is no copper (Cu) loss and primary side has small amount of no load current hence small copper loss is there which can be ignored.In this way,open circuit test is carried out in the transformer.
TRANSFORMER ON NO-LOAD
When there is no load connected in secondary side operation of transformer is called no load operation in the case of transformer draw a small amount of current which is called no-load current (Io). No-load current is 5% to 10% of full load current.No load current is utilized for magnetizing to core and eddy current loss the hysteresis loss.It means Io has two component one is magnetizing component (Iu) and another is working component (Iw).Now from phasor diagram
Io=..
Iw=Iocos..
where cos is power factor in no load case and.. is phase angle between V1 and Io.Now power consumed on no-load operation
P=V1Iocos..
TRANSFORMER ON LOAD
When certain load is connected to transformer load current I2 start to flow in secondary coil.This current will set up () flux in the core in opposite direction to no-load flux ().() will link to primary winding and induced some voltage in the primary coil decreases.Now potential difference between supply and winding voltage will be increased.Hence additional current I2 will start to flow in addition to Io in primary side. Amount of I2 depends on amount of I2.Now I2 in primary side sets up into its own flux ().Hence () and () get conduced each other resulting only () in the core.Therefore in this transformer flux remains constant in the core.
N2I2=N1I2
N2/N1=I2/I2
Transformer
Transformer is that electrical machine which transfer electrical energy from one part to another part (i.e primary winding to secondary winding) without changing the frequency of the supply by the use of transformer voltage level can be increased or decreased.
Principle or operation
The winding where input is given is called primary winding and from where output is taken out that winding is called secondary winding.There is no electrical connection to common core.
Voltage available in primary winding is called primary voltage (V1).Similarly voltage in secondary side is called secondary voltage (V2).N1 is the no. of turns in primary and N2 is the no. of turns in secondary.When supply is given to primary side small amount of current circulated in primary winding which produced flux and flux flow towards secondary winding through a core made of silicon steel. The flux in the core made of silicon steel. The flux in the core made of silicon steel.The flux in-the core comes in contact with secondary winding and voltage is induced according to Faraday's law of electro magnetic induced. Voltage level can be increased or decreased by increasing or decreasing no. of turn in secondary side.
If voltage level of secondary side greater than primary side then the transformer is called step up transformer. If the voltage level of secondary side is lower than the primary side than the primary side then the transformer is called step down transformer.
Transformer is that electrical machine which transfer electrical energy from one part to another part (i.e primary winding to secondary winding) without changing the frequency of the supply by the use of transformer voltage level can be increased or decreased.
Principle or operation
The winding where input is given is called primary winding and from where output is taken out that winding is called secondary winding.There is no electrical connection to common core.
Voltage available in primary winding is called primary voltage (V1).Similarly voltage in secondary side is called secondary voltage (V2).N1 is the no. of turns in primary and N2 is the no. of turns in secondary.When supply is given to primary side small amount of current circulated in primary winding which produced flux and flux flow towards secondary winding through a core made of silicon steel. The flux in the core made of silicon steel. The flux in the core made of silicon steel.The flux in-the core comes in contact with secondary winding and voltage is induced according to Faraday's law of electro magnetic induced. Voltage level can be increased or decreased by increasing or decreasing no. of turn in secondary side.
If voltage level of secondary side greater than primary side then the transformer is called step up transformer. If the voltage level of secondary side is lower than the primary side than the primary side then the transformer is called step down transformer.
(1) It protects armature conductor from short circuit.At starting position of motor.It cannot rotates immediately due to inertia at that time N=0, and Eb=a. Thus maximum current is flow from the armature.
(2) It helps to produce required amount of torque.When motor is over loaded it's speed decreases and then Eb also decreases but Ia increase Eb=Z
So the motor develops more torque to over come additional load.Similarly when the motor is under loaded,it is speed increases and Eb also increases but Ia decrease so the motor develop less torque to compensates the respective load.In every energy conversion their must be an opposing agent in this case Eb.Opposes the source voltage V.d So that the source V has to supply current against the Eb and the cause to rotate the armature and hence electrical energy is converts in mechanical energy.
(2) It helps to produce required amount of torque.When motor is over loaded it's speed decreases and then Eb also decreases but Ia increase Eb=Z
So the motor develops more torque to over come additional load.Similarly when the motor is under loaded,it is speed increases and Eb also increases but Ia decrease so the motor develop less torque to compensates the respective load.In every energy conversion their must be an opposing agent in this case Eb.Opposes the source voltage V.d So that the source V has to supply current against the Eb and the cause to rotate the armature and hence electrical energy is converts in mechanical energy.
Characteristics of DC motor
The characteristics curve of a motor are those curves which show relation ships between the following quantities.
(1) Torque and armature current (Ta/Ia) characteristics
(2) Speed and armature current (N/Ia) characteristics
(3) Speed and torque (N/Ta)
Characteristics of series motor:
(1) Ta/Ia characteristics:
In series motor field winding also carry the armature current.Therefore Ia is proportional to flux upto the point of magnetic saturation.
At the decreasing load Ia and flux is small.But as Ia is increase.Ta decrease as the square of the current.Hence Ta/Ia curve is a parabola. After saturation flux is almost independ of Ia.Hence Ta is directly proportional to Ia only so tje characteristics becomes straight lines.The shaft torque (Tsh) is less than armature torque due to stray loss.After saturation flux is constant over the Ia is increases.
(2) N/Ia characteristics
When load is heavy Ia is large.Hence speed is low this decrease Eb.Hence increasing Ia decrease Eb.But small Ia speed varies inversely as armature current.DC series motor has higher starting torque and low speed so it is useful for traction purpose like trolly bus, electirc train, roapway, machine.
(3) N/Ta characteristics
When torque is increased,armature has the supply more,current and Ia=If and hence flux increases but Eb decrease resulting low value of speed.When the torque is decrease or no load or light load condition the armature or field draws very low value of current and flux will be very low.So the speed is dangerously high.Therefore it is said that dc series motor should never be start on without load.
The characteristics curve of a motor are those curves which show relation ships between the following quantities.
(1) Torque and armature current (Ta/Ia) characteristics
(2) Speed and armature current (N/Ia) characteristics
(3) Speed and torque (N/Ta)
Characteristics of series motor:
(1) Ta/Ia characteristics:
In series motor field winding also carry the armature current.Therefore Ia is proportional to flux upto the point of magnetic saturation.
At the decreasing load Ia and flux is small.But as Ia is increase.Ta decrease as the square of the current.Hence Ta/Ia curve is a parabola. After saturation flux is almost independ of Ia.Hence Ta is directly proportional to Ia only so tje characteristics becomes straight lines.The shaft torque (Tsh) is less than armature torque due to stray loss.After saturation flux is constant over the Ia is increases.
(2) N/Ia characteristics
When load is heavy Ia is large.Hence speed is low this decrease Eb.Hence increasing Ia decrease Eb.But small Ia speed varies inversely as armature current.DC series motor has higher starting torque and low speed so it is useful for traction purpose like trolly bus, electirc train, roapway, machine.
(3) N/Ta characteristics
When torque is increased,armature has the supply more,current and Ia=If and hence flux increases but Eb decrease resulting low value of speed.When the torque is decrease or no load or light load condition the armature or field draws very low value of current and flux will be very low.So the speed is dangerously high.Therefore it is said that dc series motor should never be start on without load.
Types of DC motor
There are three types of DC motor.They are:
(1) Series motor
(2) Shunt motor
(3) Compound motor
(1) Series motor
In series motor the winding is joined in series with the armature
conductors.As they carry full load current, field winding consists of a few turns of thick wire.
In series motor supply current I is equal to field current (If) and armature current (Ia) if (Ra) be armature winding resistance and (Rf) be field winding resistance.
I=Ia=If-(1)
V=Eb+(+,-)If Rf+Ia Ra-(2)
=Eb+I (Rf+Ra)-(3)
I=(V-Eb/Rf+Ra)-(4)
(2) Shunt motor:
In shunt motor field winding are connected across or in parallel with the armature conductor.Shunt field winding have maximum resistance.It is wounded many turns with thin wire.The same applied volt
age is available in both armature and field winding.
In this type of motor
I= Ia+If-(1)
If= V/Rf-(2)
V= (Eb+Ia Ra)-(3)
Ia= (V-Eb/Ra)-(4)
(3) Compound motor:
In compound motor both shunt and series field is stronger than series field.When the series field flux aids the shunt field flux then motor is said to be commutativity compound motor in which fluxes and series are added.
On the other hand if series field opposes the motor is said to be differentially compound in which the fluxes series are subtracted.
There are three types of DC motor.They are:
(1) Series motor
(2) Shunt motor
(3) Compound motor
(1) Series motor
In series motor the winding is joined in series with the armature
conductors.As they carry full load current, field winding consists of a few turns of thick wire.In series motor supply current I is equal to field current (If) and armature current (Ia) if (Ra) be armature winding resistance and (Rf) be field winding resistance.
I=Ia=If-(1)
V=Eb+(+,-)If Rf+Ia Ra-(2)
=Eb+I (Rf+Ra)-(3)
I=(V-Eb/Rf+Ra)-(4)
(2) Shunt motor:
In shunt motor field winding are connected across or in parallel with the armature conductor.Shunt field winding have maximum resistance.It is wounded many turns with thin wire.The same applied volt
age is available in both armature and field winding.In this type of motor
I= Ia+If-(1)
If= V/Rf-(2)
V= (Eb+Ia Ra)-(3)
Ia= (V-Eb/Ra)-(4)
(3) Compound motor:
In compound motor both shunt and series field is stronger than series field.When the series field flux aids the shunt field flux then motor is said to be commutativity compound motor in which fluxes and series are added.
On the other hand if series field opposes the motor is said to be differentially compound in which the fluxes series are subtracted.
Motor is an electrical machine which converts the electrical energy into the mechanical energy.
It's action is based on the principle that when a current carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Flemming's left hand rule.Constructionally there is no difference between DC motor and DC generator.
When the DC supply is provided to field pole through field winding so that it produces uniform magnetic field in between the field poles where armature is placed.Again the DC supply is feed to armature winding through carbon brush and commutator segments, the current enters through C1X1B and comes out through A1Y1C2.Then by principle when current carrying armature winding placed in magnetic field ,the armature experiences a force and hence it rotates in clock wise direction (due to Flemming's left hand rule).
After 180 degree rotation the commutator segments change it's position therefore the direction of current is same and hence the motor rotates in same direction i.e,clockwise direction.
It's action is based on the principle that when a current carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Flemming's left hand rule.Constructionally there is no difference between DC motor and DC generator.
When the DC supply is provided to field pole through field winding so that it produces uniform magnetic field in between the field poles where armature is placed.Again the DC supply is feed to armature winding through carbon brush and commutator segments, the current enters through C1X1B and comes out through A1Y1C2.Then by principle when current carrying armature winding placed in magnetic field ,the armature experiences a force and hence it rotates in clock wise direction (due to Flemming's left hand rule).
After 180 degree rotation the commutator segments change it's position therefore the direction of current is same and hence the motor rotates in same direction i.e,clockwise direction.
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