Secondary Storage Devices Magnetic Tape Cassette Tape If

Secondary Storage Devices

Magnetic Tape Cassette Tape If the magnetic material is exposed to a magnetic field, then it can permanently magnetised by this field. Magnetic Tape In a 90 minute cassette tape, there will be 135 metres of magnetic tape running at 4. 76 cm/s across the roller. Secondary Storage Devices Magnetic medium (Ferromagnetic material, Fe. O) Plastic base

Magnetic Tape The magnetic tape passes under an iron coil in a linear motion. It continues to move with a series of N-S and S-N polarities that are stored on the magnetic material. Magnetic Head As the tape moves, an induced magnetic field is set up in the iron core. The changes in this induced magnetic field causes a changing current (voltage). This shows the spools and the read/write head of the tape. Secondary Storage Devices Magnetic tape causing electric charge to flow

Hard disk The hard disk works on similar lines to the magnetic tape, using a magnetic medium to store data. However, there are some crucial differences: 1. The material used in magnetic tape is a flimsy, bendy plastic material. In a hard drive it is hard and polished on a high precision aluminium or Hard disk glass disk. The size of data therefore can be stored in very small domains 2. The read/write head using a magnetic tape touches the surface of the tape. On the hard drive it hovers a fraction above the surface. 3. The read/write head on a magnetic tape device moves about 4. 76 cm/sec, so sequential searching makes finding data slow. Contrast this with the hard drive, that spins at 170 mph (or 7501 cm/sec) and retrieving data appears instant. Magnetic tape causing electric charge to flow Secondary Storage Devices

Hard disk The hard disk works on similar lines to the magnetic tape, using a magnetic medium to store data. Read/write head 2 mm by 3 mm The read/write head hovers over the platter (eg 10 s nm above) and Magnetic material (10 -20 nm) Aluminium alloy or glass about How the read/write head identifies the data. Secondary Storage Devices Read/write head

Hard disk The diagram below shows how data is accessed in more detail. Secondary Storage Devices