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A hard disk drive (HDD)[note 2] is a data storage device used for storing and retrieving digital information using rapidly rotating discs (platters) coated with magnetic material. An HDD retains its data even when powered off. Data is read in a random-access manner, meaning individual blocks of data can be stored or retrieved in any order rather than just sequentially. An HDD consists of one or more rigid ("hard") rapidly rotating discs (platters) with magnetic heads arranged on a moving actuator arm to read and write data to the surfaces.
Introduced by IBM in 1956,[1] HDDs became the dominant secondary storage device for general purpose computers by the early 1960s. Continuously improved, HDDs have maintained this position into the modern era of servers and PCs. More than 200 companies have produced HDD units, though most current units are manufactured by Seagate, Toshiba and Western Digital. Worldwide revenues for HDDs shipments are expected to reach $38 billion in 2012, up about 19% from $32 billion in 2011.
The primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000: a 1-terabyte (TB) drive has a capacity of 1,000 gigabytes (GB; where 1 gigabyte = 1 billion bytes). Typically, some of an HDD's capacity is unavailable to the user due to use by thefile system and the computer operating system, and possibly inbuilt redundancy for error correction and recovery. Performance is specified by the time to move the heads to a file (average access time) plus the time it takes for the file to move under its head (average latency, a function of the physical rotational speed inrevolutions per minute) and the speed at which the file is transmitted (data rate).
The two most common form factors for modern HDDs are 3.5-inch in desktop computers and 2.5-inch in laptops. Different sizes are used in specialty devices such as portable media players or in some server hardware. HDDs are connected to systems by standard interface cables such as SATA (Serial ATA), USB or SAS (Serial attached SCSI) cables.
As of 2012, the primary competing technology for secondary storage is flash memory in the form of solid-state drives (SSDs). HDDs are expected to remain the dominant medium for secondary storage for the forseeable future due to advantages in recording capacity and price per unit of storage,[2][3] but solid state drives are replacing rotating hard drives especially in portable electronics where speed, physical size, and durability are more important considerations than price and capacity.[4][5]
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Why does the short-circuit test essentially show only PR losses and not excitation losses in a transfonner?
Because a short-circuit test is done at low voltage so there is very small power loss in the magnetic core. That is because there is very magnetic flux.
Why does the primary coil of a transformer not short circuit when AC voltage is applied?
Because it is an inductor - inductors oppose change in current; so every time the current changes (continually in AC) the energy is transferred and becomes a changing magnetic field - and according to various laws these magnetic fields oppose the current and limit it - so doesn't act as a short. DC sees the resistance of the coil only (low R) but not the inductance, as there is no change with DC - so DC sees it as a short........
What are the safety features available in a breaker?
To detect and open the circuit if a thermal overload is present and to detect and open the circuit if a short circuit caused by a magnetic increase of flux in the circuit.
What is magnetic balance test of transformer?
The Magnetic Balance test is conducted on Transformers to identify inter turn faults and magnetic imbalance.
What happens to the magnetic field if the current in the wire increases?
If the current in the wire increases, the magnetic field also increases.
What uses short bursts of a magnetic field to produce images?
the magnetic resonance imaging, also abbrieviated as: M.R.IA digital camera uses short bursts of a magnetic field to produce images. The images are then stored on a disk or other memory source within the camera. The disk can then be inserted into most computers to download the images.
Is a magnetic device used to store information?
It is the magnetic elements in a magnetic disk that are used to store information.
Which year computer use to magnetic disk?
computer use to magnetic disk which generation
Use magnetic particles to store items on a disk surface?
magnetic disk
Write a short note on magnetic disk?
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders. A device that stores computer data on magnetic tape is a tape drive.
How does a magnetic disk work?
Digital information is stored in microscopic needles as part of the disk's magnetic coating.
Is floppy disk considered magnetic media?
In a way, yes. The material that makes up the "disk" in a floppy is Mylar, a magnetic substance. Data is stored on the Mylar disk in the form of magnetic charges.
What is a device that puts information on a magnetic disk?
A disk drive.
What do you call the subdivision of a track on magnetic disk or optical disk?
A sector
Magnetic Disk Performance?
help!
Data is written to and read from a floppy disk via a magnetic?
Yes, data is written to and read from a floppy disk using a magnetic read/write head that interacts with the magnetic coating on the disk. When writing data, the magnetic head aligns the magnetic particles on the disk surface to represent the information. When reading data, the head detects the magnetic orientation of the particles to retrieve the stored information.
Hard disk floppy disk and tape storage technologies can be classified as?
magnetic
