Output Devices

Q1. a)  What is a meant by  Output Device ? 

✬  An Output device is a hardware device which converts information into human readable form.

b)  List out the output devices used in computer system.

• Monitor.
• Printer.
• Projector.
• Interactive Whiteboard / Smart board
• Headphone.
• Speaker.

Computer Monitors :

Q2.  What is  Computer Monitor  and list out the types of monitors we have ?

A computer monitor is an output device that displays information in pictorial form.

✬  CRT (cathode ray tube) monitor.

✬  Flat Screen monitors.

1. LCD (liquid crystal display) monitor.
2. LED (Light Emitting Diode) Monitor.
3. TFT - LCD (Thin Film Transistor - LCD) Monitor.
4. OLED (Organic Light Emitting Diode) Monitor.

Q3.  What is a  CRT (Cathode Ray Tube)  Monitor.

⇒  CRT use cathode ray tubes (CRTs) containing an electron gun at the back of the tube which fires electrons at groups of phosphor dots coated inside of the screen.

⇒  When the electrons strike the phosphor dots they glow to give the colours to form an image.

Q4. a)  Describe  LCD (Liquid Crystal Diode/Display)  Monitor.

⇒  LCD is made up of a layer of liquid crystal diodes, sandwiched between two polarizing material sheets.

⇒  It uses back lighting from cold cathode fluorescent lamp (CCFL), that illuminates the LCD panel.

⇒  Liquid crystal diodes are grouped together with three primary colours (Red, Green and Blue), to form a full colour pixel.

⇒  When an electric current is passed through the LCD panel, the liquid crystals aligns itself to allow only the required light to pass and form the image on the screen.

 Note (for little detail understanding) :    LCD is a combination of two states of matter, the solid and the liquid. They have both the properties of solids and liquids. As in liquids, the molecules of a liquid crystal can flow past one another. As in solid crystals, however, they arrange themselves in recognizably ordered patterns.

In LCD panel, the molecules of liquid crystals align themselves with their axes in parallel to the direction of polarized light, so that the light is allowed to pass through it. This polarized lights are blocked at the front polarized sheet perpendicular to the direction of the light.

When an electric field (induced by a small electric voltage) is applied, liquid crystals molecules changes its orientation and twists the light's angle passing through them. This change in the angle of light, allows it to pass through the top polarizing filter to form image on the screen.

b)  Give two advantages and disadvantages of LCD monitors.

✬   Advantages : 

1. Lightweight and compact than CRT.
2. Very low-power consumption than CRT.
3. It is not affected by magnetic field.
4. It do not generate heat like CRT.

✬   Disadvantages : 

1. Poor viewing angle.
2. Motion blur is common.
3. It has fixed resolution.

Q5.  Many computer monitors are advertised as LED when in fact they are LCD screens which are backlit using LEDs.

a)  Describe  LED (Light Emitting Diode/Display)  back-lit Monitor.

⇒  LED back-lit monitor uses LCD technology, but instead of CCFL back light, it uses an array of LEDs as back light to illuminate the LCD panel.

⇒  LED back-lit monitor is thinner and more energy efficient than LCD monitor.

⇒  It provides better contrast and color quality for a sharper image.

b)  Give two advantages and disadvantages of LED monitors.

✬   Advantages : 

1. LED back-lit monitor reaches maximum brightness quickly.
2. LED back-lit monitors are lighter and thinner than LCD monitor.
3. They produces high quality display with vivid colours and higher contrast.
4. It consumes less power than LCD.

✬   Disadvantages : 

1. LED is expensive than LCD.
2. Poor viewing angle.
3. It has fixed resolution.
4. Motion blur is common.

Q6. a)  Describe  TFT-LCD (Thin Film Transistor - LCD)  Monitor.

⇒  A TFT monitor uses thin-film transistor technology in an LCD display.

⇒  LCD panel is coated with a thin film of transparent semiconductor silicon layer that works as transistors.

⇒  Each pixel of LCD panel is controlled by a separate tiny transistor, to give full colour, high resolution and more contrast.

b)  Give two advantages and disadvantages of TFT monitors.

✬   Advantages : 

1. Control of thin film transistors over each pixel gives best resolution and higher image quality.
2. The resolution of LCD can be changed.

✬   Disadvantages : 

1. Poor viewing angle.
2. While the colours are beautiful they aren’t always very accurate.

Q7.  Describe how pure surface mounted  LED Screen  display images.

⇒  LED screen uses an array of tiny light emitting diodes (LEDs) as pixel.

⇒  Each pixel is formed by the group of red, green and blue LEDs.

⇒  By varying the electric current sent to each LED, its brightness can be controlled, producing a vast range of colours.

⇒  This type of screens are used for large outdoor displays due to the brilliance of the colours produced.

Q8. a)  Describe  OLED (Organic Light Emitting Diode)  Monitor.

⇒  OLED display uses a thin layer of Organic light emitting diodes, made up of organic compound which acts as semi-conductors.
(e.g. polyaniline and polyfluorene)

⇒  This flexible Organic films is sandwiched between two charged electrodes, made up of rigid glasses or flexible polymers.

⇒  When an electric field is applied to the electrodes, OLED gives its own light to form the image on the screen.

b)  Give two advantages and disadvantages of using OLED monitors compared to existing LEDs and LCDs.

✬   Advantages : 

1. It is very thin and flexible to be bend to any shape.
2. It provides larger viewing angle (about 170 degrees).
3. Since it requires no backlighting, it uses very less power than LCD.
4. It provides brighter image with higher contrast (superior image quality).

✬   Disadvantages : 

1. Organic materials used degrades over time, like any organic matter.
2. It require more power when displaying documents with white or bright backgrounds.

Q9.  Distinguish the difference between TFT-LCD and OLED monitors.

⇒  TFT-LCD uses LCD backlight technology, whereas OLED do not use backlight.

⇒  OLED uses a thin flexible layer of organic light emitting diodes that emits light when an electric field is applied.

⇒  TFT-LCD Monitors gives full colour, higher resolution and contrast, as each pixel on the screen is controlled by its own transistor.
But view angle is poor.

⇒  OLED provides increased brightness, higher contrast and large perfect viewing angle, than TFT-LCD monitors.

Q10.  Describe  how Inkjet printer could reduce the manufacturing cost of OLED screens. 

⇒  Currently, the OLED screens are built using an evaporation process which is much more problematic and expensive.

⇒  In future this outdated technique could be replaced by Inkjet printing technology.

⇒  Inkjet printer could create a patterned films by spraying organic OLED liquid, unlike mask-dependent evaporation process.

⇒  Benefits of Inkjet printing include lower production costs, fewer defects, manufacturing flexibility, and scalability to large-size panels.

Interactive White-board / Smart Board :

Q11. a)  Describe  Interactive Whiteboard / Smart Board. 

⇒  Interactive Whiteboard (IWB) is a classroom tool, that allows images from a computer screen to be displayed on the board using Digital Projector.

⇒  When connected to the computer with special IWB-software, it transforms into touch sensitive board.

⇒  The user can write, edit and click the elements to manipulate the content with a special pen or with his finger.

⇒  The text or drawings produced are then stored in an electronic form for later use.

⇒  With the computer connected to the internet, teachers and students can access and share information around the world.

⇒  It helps the student to engage in lessons by working collaboratively.

b)  How are smart boards beneficial in the classroom ?

1. Enhanced Lessons : Integrate various learning styles into one experience. Students can learn better and remember more by seeing, hearing, and interacting with the board through touch.
2. Interactive Learning : Allow children to interact with the learning material through touching, drawing, or writing on the board. Educational games can be played by entire classrooms.
3. Low Maintenance : No chalk or markers are needed. Data is modified using a specialized pen for highlighting, drawing, and writing. No cleanup. It’s just that easy.
4. Flexibility in the Classroom : Various media types can be displayed, whether photos, graphs, maps, illustrations, or videos- teachers have an abundance of options. You can create creative lessons to inspire your students.
5. Connected to the Internet : Teachers have access to various sources to enhance and support their lessons.
6. Integrated Technology : Any device you can think of like computers, microscopes, cameras, and video cameras can be attached to the boards to enhance instruction.

LCD & DLP Projectors :

Projectors are used to project computer output on larger screen or interactive whiteboards.

Projectors comes in two different types :

1. LCD Projector (Liquid Crystal Display projector).
2. DLP Projector (Digital Light Projectors).

Q12. a)  Describe  LCD Projector ?

✬  LCD Projector uses LCD display technology.

✬  It contains three LCD panels, each pannel creates an image using just one of the primary colors (red, green, and blue).

✬  All three colored images are combined to form full color image and projected on the screen at once.

b)  Describe how LCD Projector works.

⇒  LCD projectors work by using three LCD panels, a lamp, a prism, and polarizing filters to create the image on the screen.

⇒  A high intensity white back light from CCFL or LED is beamed, and passed through a polarizing filter.

⇒  These polarized light is then sent to a series of dichromic mirrors, which reflects the light at different wave length corresponding to Red, Green and Blue light.

⇒  These different coloured light passes through three different LCD panels to produce three different coloured images.

⇒  These images are then combined using a special dichromic Prism, allowed to pass through a projector lens and produce a full colour image onto the big screen.

c)  Give two advantages and disadvantages of LCD Projector.

✬   Advantages : 

1. LCD projector are less expensive than DLP.
2. LCD projector produces sharper image than DLP.
3. LCD projector has no moving parts.

✬   Disadvantages : 

1. LCD projector has lower contrast ratio than DLP.
2. LCD panels being organic, they degrade over time.

Q13. a)  Describe  DLP (Digital Light Processing) Projector ?

✬  DLP projector uses millions of micro-mirrors arranged on DLP chip that creates pixels on screen.

✬  A bright white light source is beamed through a spinning colour filter on DLP chip.

✬  The white light is split into a sequence of primary colours red, green and blue.

✬  When the micro-mirror tilt towards the light source to reflect light on the screen, the pixel is ON and when tilt away, the pixel is OFF.

✬  This creates light and dark pixels of millions of coloured shades to produce an image on the screen.

b)  Give two advantages and disadvantages of DLP Projector.

✬   Advantages : 

1. DLP provides higher contrast ratio.
2. DLP projectors are lighter and portable.
3. DLP projectors require less maintenance than LCD projectors because of sealed chip design.

✬   Disadvantages : 

1. DLP projectors aren't as good as LCD models at rendering colours.
2. DLP projector could suffer from the "Rainbow effect" (This is due to the slow spinning speed of Chromatic Colour filter Wheel).

2D and 3D Printer / Cutter :

Q14. a)  What is an  Inkjet Printer ?

Inkjet printer is an output device that accepts processed information like, text and graphics from a computer, and recreate it by spraying droplets of ink on paper or plastic substract.

It essentially contains :

⇒  a Print-head, which consists of nozzles that spray droplets of ink onto the paper to form characters and images.

⇒  an Ink cartridge containing all three primary colours and black colour ink.

⇒  a stepper motor and belt, which moves the print head assembly across the page from side to side.

⇒  a paper feeder, which automatically feeds the printer with papers as they are required.

b)  State two suitable applications for Inkjet Printer.

1. Home and Office print jobs, where only a few pages of good quality, colour printing is needed.
2. Photo studio print jobs, where high quality photos to be printed.
3. Printing posters of large.
4. Printing architecture and engineering drawings using plotter that uses Inkjet technology.
5. Printing 3D prototypes using 3D Printer that uses Inkjet technology.

c)  Give two advantages and disadvantages of Inkjet Printer.

✬   Advantages : 

1. Provides Low cost printing.
2. High quality printing with vivid colours.
3. Could print over different types of flexible and solid surface.
4. Don't need warm up time.

✬   Disadvantages : 

1. It is not fit for large scale printing, as it contains small Ink cartridge.
2. Printing speed is not as fast as laser printers.
3. Print head is less durable, prone to clogging and damage.

Q15.  Ink-jet Printer contains print head nozzle, which sprays ink droplets on the paper using the following two technologies ;

• Thermal Bubble technology
• Piezoelectric technology

a)  Describe  Thermal Bubble technology. 

⇒  Thermal Bubble Ink-jet contains tiny resistors at the nozzle of ink reservoir that creates heat to vaporize ink.

⇒  The vaporized ink forms a tiny bubble which when expands ejects the ink from the print head to the paper.

⇒  When the bubble collapses, it creates a small vacuum which allows fresh ink to be drawn into the print head.

⇒  This continues until the printing finishes.

b)  Describe  Piezoelectric technology. ?

⇒  Piezoelectric Ink-jet contains a crystal, located at the back of each nozzle of the ink reservoir.

⇒  The crystal is given a tiny electric charge which makes it to vibrate.

⇒  The vibration forces the ink to be ejected on the paper and at the same time more ink is drawn in for further printing.

⇒  This continues until the printing finishes.

Q16.  Give different stages of printing process of an Ink-jet printer.

Stage	Description of what happens
1.	The data from the document is sent to the printer driver.
2.	The printer driver ensures that the data is in a format that the chosen printer can understand.
3.	A check is made by the printer driver to ensure that the chosen printer is available to print.
4.	The data is then sent to the printer and is stored in a temporary memory known as printer buffer.
5.	A sensor detects whether paper is available in the paper feed tray. If it is out of paper then an interrupt signal is sent to the computer to produce an error message.
6.	As the paper is fed through the printer, the print head moves from side to side across the paper to spray ink and print the text or graphics stored in buffer.
7.	When buffer get empty, the printer sends an interrupt to the processor requesting for more data if any.
8.	The whole process is repeated until the whole document is printed.

Q17. a)  What is  Laser printer  ?

Laser printer is an output device that produces a high quality printout by using a laser beams, to form a pattern of electrostatically charged dots on a light-sensitive drum, which attract dry powder ink called toner. The toner is transferred to a piece of paper and fixed by a heating process.

Unlike Inkjet printer, Laser printer prints the whole page in one go.

b)  Describe the  printing process of Laser printer  (Laser printing technology).

⇒  Laser printer uses electrostatic charge for printing.

⇒  It produces high quality printout by passing Laser beams of text and graphics over a positively charged cylindrical drum.

⇒  The bright parts of the drum lit by the projected image lose their charge and leaves negatively charged area, but the dark areas keep the positive charge.

⇒  A black carbon powder called toner is positively charged.

⇒  The toner is attracted to the negatively charged area of the drum.

⇒  The drum rotates and rolls against a piece of negatively charged paper.

⇒  The toner is transferred from the drum to the paper making a black and white image of the original.

⇒  The paper is heated which makes the toner stick to it permanently.

c)  State two suitable applications of Laser Printer.

1. Company and Office print jobs, where very fast, large volume of high quality printing is needed.
2. Producing a large numbers of high-quality flyers or pamphlets for advertising.
3. Large scale Book and magazine printing.

d)  Give two advantages and disadvantages of Laser Printer.

✬   Advantages : 

1. Suitable for large scale bulk printing.
2. High quality printouts better than ink-jet.
3. Prints faster than ink-jet.
4. Cost per page is cheaper than ink-jet.
5. Prints very quietly without any sound than ink-jet.

✬   Disadvantages : 

1. It is expensive than Inkjet printer.
2. Larger and heavier than ink-jet printers
3. Toner is more expensive than ink-jet cartridges.

Q18.  Give different stages of printing process of Laser printer.

Stage	Description of what happens
1.	The data from the document is sent to the printer driver.
2.	The printer driver ensures that the data is in a format that the chosen printer can understand.
3.	A check is made by the printer driver to ensure that the chosen printer is available to print.
4.	The data is then sent to the printer and is stored in a temporary memory know as printer buffer.
5.	The printing drum is given a positive charge.
6.	As the printing drum rotates, a Laser image of the document is beamed over the drum to remove the positive charge and leaves negative charge in that area.
7.	Negatively charged areas exactly matches with the text and image to be printed.
8.	The printing drum is rolled over positively charged Toner; this is then sticks to the negatively charged parts of the drum.
9.	A negatively charged paper is then rolled over the printing drum.
10.	The Toner on the printing drum is now transferred to the paper to reproduce the required text and image.
11.	The paper goes through a fuser which melts the toner so it fixes permanently to the paper.

Q19. a)  Describe  3D Printer. 

⇒  3D printer is used to produce three-dimentional solid object, using additive layer manufacturing and Inkjet technology.

⇒  The digital computer model of the object to be printed is created by using a 3D scanner, or by using CAD software (which provides the dimensions and shape of the object).

⇒  The solid object is built up spraying powdered resin (synthetic organic polymer), metal or ceramic, layer over layer from bottom to top successively until final object is produced.

b)  Give difference between  Direct  and  Binder  3D printer.

✬   Direct 3D Printer : 

⇒  Direct 3D printer uses Inkjet technology, in which print head moves horizontally (left and right) and vertically (up and down) as in normal printer.

⇒  It uses only one pass to spray powdered material for each layer.

✬   Binder 3D Printer : 

⇒  Binder 3D printer is similar to Direct 3D printer, but it uses two passes, one pass for spraying powdered material and another pass to spray binder (a type of glue) to harden the raw material.

c)  State three suitable applications for 3D Printer.

1. Industrial manufacturing - for printing prototypes and functional parts of machines.
2. Medical industry - for producing artificial organs, like teeth, ears, legs, etc.
3. Education - printing prototypes for students to use in classes and projects.
4. Art and Jewelry making.

d)  Give two advantages and disadvantages of 3D Printer.

✬   Advantages : 

1. Produce prototypes quickly.
2. Low development cost.
3. Easy to spot and correct design errors.
4. Any complicated objects can be printed with variety of materials.
5. Computer designs can be shared and printed by others.

✬   Disadvantages : 

1. 3D printer are expensive to buy.
2. Anyone can print dangerous items (like guns) without being checked.
3. Copyright issues - it is very easy to print illegal copies of items, if you have its design.

Q20.  Give different steps of producing an object using 3D Printer.

Stage	Description of what happens
1.	A drawing is made using CAD (Computer Aided Design) software.
2.	Finalized 3D drawing is imported into a 3D printer software that prepares it in a format which 3D printer could understand.
3.	The 3D printer is setup to allow the solid object to be made.
4.	The solid object is built up by spraying powdered material layer over layer until it attains fully shaped object.
5.	The object is removed from the printer and washed by water or sand to remove excess waste material.

Q21.  3D objects could be produced using 3D Cutter.

a)  Describe  3D Cutter. 

⇒  3D Cutter uses subtractive fabrication technique.

⇒  It removes the excess material from the solid block to give the shape of the object.

⇒  It uses Laser beams to simply cut a given material perfectly and clean and polish the object.

b)  State three suitable applications of 3D Cutter.

1. Laser surgery - to remove unwanted tissues from the body.
2. Industrial manufacturing - to produce laser cut products with metals like, steel, tungsten, nickel, brass and aluminium.
3. Laser engraving and laser marking - used to mark or engrave all varieties of jewelry.
4. Laser cut ceramics - to produce artifacts and sculptures.

c)  Give two advantages and disadvantages of 3D Cutter.

✬   Advantages : 

1. Laser cutting offers fast, clean and accurate cuts even for small complex details.
2. Laser cutting offers freedom for the design and the quantities of product.
3. All sides of an object can be cut into

✬   Disadvantages : 

1. Can be expensive to setup and maintain.
2. Output is only as good as a the computer 3D model

Q22.  Andrew wants to produce small 3D model of his company logo.

Explain  how a 3D Cutter could be used to produce the 3D model of the logo. 

Stage	Description of what happens
1.	A digital design or drawing of the company logo is created using CAD (Computer Aided Design) software. (which provides the dimension and shape of the object)
2.	Finalized 3D drawing is imported into a special software that prepares it in a format which 3D Cutter could understand.
3.	A raw solid block of metal or plastic is loaded on the 3D Cutter.
4.	A Laser beam is used to cut and remove unwanted excess material by moving along X, Y and Z-axis to give the required shape of the object.

Speakers and Headphones :

Q23. a)  What are  Loudspeakers and Headphone ?

⇒  Loud Speakers and Headphone are the output devices responsible for producing sounds.

⇒  It converts digital sound signals into analogue waves that are audible to our human ear drums.

⇒  It allows us to hear music, communicate with people through voice and video calls, get computer warning signals etc.

b)  Describe  how a Loudspeaker works. 

1. Speaker works by converting electrical energy into mechanical energy that compresses the air to produce sound.
2. When an audio signal in the form of electric current is sent through the voice coil wrapped around an iron core.
3. The voice coil generates magnetic field in the iron core, which is attracted and repelled by the permanent magnet around it.
4. The vibration of iron core attached to the paper cone, causes the cone to vibrate to produce the sound.

c)  Describe how the music, which is digitally stored can be played through a pair of analogue loudspeakers.

1. Digital sound stored on a file is passed through a digital to analogue converter (DAC), where it is changed into an electric current.
2. This is then passed through an amplifier which increases the voltage of the sound signal large enough to drive a loudspeaker.
3. This electric current is then fed to a loudspeaker where it is converted into sound.