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How hardware devices work
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- 1How does hard disk drive work?Magnetic medium
May have multiple platters
One head per platter
Disk divided into tracks and sectors
Disk continually spinning at a high speed
The medium is in a sealed enclosure - 2Give one development in the design of hard disk drives that has enabled this increase in storage capacity.More platters
More tracks on a platter
Smaller read/write heads
Greater density of data on each platter - 3State a reason why you might choose the solid-state drive.Silent operation
Are lighter
Less heat generated
Less power required/longer battery life
Faster access speed - 4DVD disks are the same physical size as a CD. Why is the storage capacity for a DVD disk far larger than that of a CD?Recorded pit size is much smaller.
Different wavelength of lasers.
DVD multi-layered/double sided.
Length of track on DVD is longer. - 5Describe how data is written to and read from a CD-R disk.To write data, a high powered/high frequency laser makes sections less reflective/burns a pit.
A low powered laser is used to read data back from the disk.
The data is stored as a continuous spiral track. - 6Compare the principles of operation of a laser printer and an inkjet printer when printing.Inkjet printer prints line by line whereas with laser printers they print by page.
The inkjet printers use four cartridges containing cyan, magenta, yellow and black ink.
The heater behind the ink reservoirs are warmed and vaporizes the droplets of ink.
The printer fires ink on the paper, after it's finished, the heater turns off and so the ink cools and sucks the remainder of droplets back.
The laser printer - the printer drum is coated in negative charge.
The laser beams are directed at the printer drum and it reminds/neutralizes the electric charge on the drum. The toner is given a negative charge and is melted to the paper by heated rollers.
The laser is turned on or off. - 7How does the RFID work?The RFID reader transmits the signal.
The signal which activates current RFID tag.
The RFID tag transmits data by radio (wave).
Physical contact between tag and reader are not required (tag must be near reader). - 8Describe the principles of operation of a flatbed scanner.The document is placed onto the glass pane.
Under which is a bright light/rows of red, green and blue and array of optical sensors.
Covered to exclude ambient light.
Sensor light moves steadily under the glass to scan the whole document.
The reflected light is converted into an equivalent electrical signal.
More light is reflected from bright regions than dark regions. - 9How does touch sensitive screen work?Beams of infra-red light is projected across the screen.
The position of e.g. finger would be detected and then the beam would be broken at a certain position.
The position matched to an action is performed by the computer. - 10Describe the principles of operation of a digital still camera.The image is captured when the shutter is pressed.
CCD used ADC to convert measurement of light intensity into binary.
Image data is usually stored on solid-state disk.
Large pixels collect more electrons than small pixels and so produce better quality images. - 11Describe the principles of operation of a bar code reader, excluding the use of the check digit.The light is shone at the bar code.
The user moves he reader across the bar code.
The light is reflected back.
White reflects more light, black reflects less light.
Data is transmitted as binary codes to computer.
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- AS Level AS Computing Fichas sobre How hardware devices work, creado por Balikkoftesi el 11/04/2015.
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- Balikkoftesi
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