chapter 3 - hardware devices Flashcards
1
Q
describe a laser printer’s operation
A
● A laser beam and a rotating mirror are used to draw an image of the page
on the photosensitive drum.
● The image is converted on the drum into an electrostatic charge.
● Electrostatic charge attracts toner.
● The charged paper is rolled against the drum.
● The oppositely-charged paper picks up the toner particles from the drum.
After picking up the toner, the paper is discharged to stop it clinging to the
drum.
● The paper passes through a fuser, which heats up the paper. The toner
melts and forms a permanent image on the paper.
● The electrical charge is removed from the drum and the excess toner is
collected.
2
Q
3D printer
A
- A 3D design is split into layers.
● The data for the first layer is transmitted to the 3D printer.
● The printers work by interpreting a set of instructions that model an object in 3D space.
● Filament, usually in the form of plastic-based resin, is extruded at heat and applied to
precise dimensions and location.
3
Q
microphone
A
- The microphone has a diaphragm / ribbon
● The incoming sound waves cause vibrations (of the diaphragm)
● …causing a coil to move past a magnet (dynamic microphone)
● An electrical signal is produced
4
Q
speaker
A
- Takes an electrical signal and translates it into physical vibrations to
create sound waves
○ An electric current in the coil creates an electro-magnetic field
○ Changes in the audio signal causes the direction of the electric current to
change
○ The direction of the current determines the polarity of the electro-magnet
//
○ changing the direction of the current changes the direction of the polarity
of the electro-magnet
○ The electro-magnet is repelled by or attracted to the permanent magnet
○ Causing the coil to vibrate
○ The movement of the coil causes the cone / diaphragm to vibrate
○ That vibration is transmitted to the air in front of the cone / diaphragm as
sound waves
○ The amount of movement will determine the frequency and amplitude of
the sound wave produced
5
Q
resistive touchscreen
A
- Has two charged plates
- When touched the pressure causes the plates to touch
- …which completes a circuit
- The point of contact is registered and the coordinates are calculated
6
Q
capacitive touchscreen
A
- Voltage is spread across the screen
- When the finger touches the screen charge is transferred to the finger and
- …a circuit is completed
- Sensors on the side of the screen detect the change
- The point of contact is registered and coordinates are calculated
7
Q
optical disk reader/writer
A
- Drive motor is used to spin the disc
- Surface consists of pits and lands, a pit representing 0 and land representing 1
- A lens focuses the laser onto the disc
- The laser beam is shone onto disc to read / write along each track
- The disc has a reflective surface that reflects light back to the sensor if it is a land, and doesn’t if it is a pit
- Encodes a bit pattern
8
Q
magnetic hard disk
A
- The disks are rotated (at high-speed)
- (Each surface of the disk) has a read/write head mounted on an arm (positioned just above the surface)
- The surface of the disk is divided into sectors
- The surface of the disk are also divided into concentric tracks / circles
- One track in one sector is the basic unit of storage called a block
- The data is encoded as a magnetic pattern for each block
- When writing to disk, a variation in the current in the head produces a variation in the magnetic field on the disk
- When reading from disk, a variation in the magnetic field on the disk produces a variation in current through the head
9
Q
solid state (flash)
A
- Uses a grid of columns and rows that has two transistors at each intersection
- One transistor is called a floating gate
- The second transistor is called the control gate
- Memory cells store voltages which can represent either a 0 or a 1
- Essentially the movement of electrons is controlled to read/write
- Not possible to overwrite existing data, you must first erase the old data then write the new data in the same location
