Explain the basic internal operation of a speaker.
- 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
Explain the basic internal operation of a hard disk drive
- The hard disk has one or more platters made of aluminium or glass
- Each surface of the platter/disk is ferrous-oxide which is capable of being
magnetised - The platters/disks are mounted on a central spindle
- 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 - Electronic circuits control the movement of the arm and hence the heads
- The surface of the platter/disk is divided into concentric tracks and sectors
- 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 magnetic field on the disk - When reading from disk, a variation in magnetic field produces a variation in
current through the head
How does a microphone capture music
- The microphone has a diaphragm
- The incoming sound waves cause vibrations
- « causing a coil to move past a magnet (dynamic microphone) //
changing the capacitance (condenser microphone) - An electric current is generated / changed
Describe the internal operation of a laser printer.
- The revolving drum is initially given an electrical charge
- A laser beam (bounces off moving mirrors) scans back and forth across
the drum - …discharging certain points (i.e. ‘drawing’ the letters and images to be
printed as a pattern of electrical charges) - The drum is coated with oppositely charged toner (which only sticks to
charged areas) - The drum rolls over electro-statically charged paper // Electro-statically
charged paper is fed (towards the drum) - The ‘pattern’ on the drum is transferred to the paper
- The paper is passed through the fuser to seal the image
- The electrical charge is removed from the drum // the excess toner is
collected
How does solid state memory work
- No moving parts
- Solid state memory is non-volatile
- Makes use of blocks / arrays of
- « Semiconductors // NAND gates // NOR gates // transistors // integrated
circuits - SSD Controller manages the components
- 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 // it is necessary to first erase the old
data then write the new data in the same location
Explain the differences between Dynamic RAM and Static RAM.
- DRAM has to be refreshed / charged and SRAM does not require a
refresh - DRAM uses a single transistor and capacitor and SRAM uses more
than one transistor - DRAM stores each bit as a charge and in SRAM each bit is stored
using a flip-flop/latch - DRAM requires higher power consumption under low levels of access,
(which is significant when used in battery-powered devices because it
requires more circuitry for refreshing) // SRAM uses less power (no
need to refresh) - DRAM less expensive to purchase (requires fewer transistors) // SRAM
is more expensive to buy (as it requires more transistors) - DRAM has slower access time/speed (because it needs to be
refreshed) // SRAM has faster access times - DRAM can have higher storage/bit/data density // SRAM has lower
storage/bit/data density - DRAM used in main memory and SRAM used in cache memory
What are differences between RAM and ROM.
RAM
* loses contents when power turned off/volatile memory/temporary memory
- stores files/data/operating system currently in use
- data can be altered/deleted/read from and written to
- memory size is often larger than ROM
ROM
* doesn’t lose contents when power turned off/non-volatile memory/permanent memory
- cannot be changed/altered/deleted/read only
- can be used to store BIOS/bootstrap
What are the benefits of embedded systems
Small in size
Consume little power
Low cost to produce
No operating system needed
Reliable
What are the drawbacks of embedded system
Hard to upgrade
Need specialist troubleshooting
Thrown away not upgraded
Less security due to access to internet
Advantages of magnetic storage over solid state
The computer will have a large number of read/write operations
because it is working all the time
.. magnetic storage has more longevity
Magnetic storage costs less per storage unit
… videos are large files and therefore very large storage capacity is
required
