History and Development
The primary computer storage medium, before the introduction of magnetic storage, was punch cards. These were paper cards on which holes were punched to indicate binary data invented by Herman Hollerith in the late nineteenth century. In June 1949, a group of scientists and engineers in IBM began working on creating a new storage device that would soon revolutionize the industry. May 21, 1952 marked the transition from punched-card calculators to electronic computers as IBM introduced the IBM 726 Tape Unit [1]. It was used to store data in IBM’s first commercial scientific computer intended to help the US military to design aircrafts [2]. Four years later, IBM made the first computer disk storage system: the 305 RAMAC drive. Although this drive could only store 5MB of data, information could be stored directly to any location on the disk surface without having to read all the information in between which was the case in magnetic tapes. This ability to access random locations had a very important effect on computer performance and enabled data to be stored and retrieved much faster than tapes. The next 60 years saw a huge progress in the magnetic storage industry from a variety of hard disks to portable memory such as cassette tapes, floppy disks and zip drives. Today, one can store even 3TB data on tiny 3.5 inch drives. This was all possible due to electromagnetism and the magnetic properties of ferromagnetic materials such as the oxides of iron[ add the magnetism part]
In 1819, a Danish physicist Hans Christian Oersted was setting up his materials for an experiment when he made a brilliant observation. He noticed that when a compass needle was brought close to a wire conducting an electric current, the n...
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...f the head. As a result, the magnetic field due to the head polarizes the magnetic particles that it passes directly through the medium and aligns them to its field. Based on the flow of electric current through the coils, the polarity of the head’s field and the field induced in the magnetic medium changes its polarity.
Consequently, as the magnetic field passes through the medium, the particles that are right below the head gap tend to align in the same direction as this field. Once the individual magnetic dipoles of the particles are aligned, they no longer cancel out and a net magnetic field is observed in that region. Many magnetic particles are now operating together to produce a cumulative field with the same direction. Due to the hysteresis properties of ferromagnetic materials, the individual particles retain their magnetic dipoles as well as the net field.
The lack of the internal drive, even 1 k drives proved to be very hard on the computers of the 1950’s (“Hackers” Internet) “with out the hard drives, programmers had
The MRI works by using hydrogen atoms’ magnetic properties within the human body to produce high quality images. These protons of the hydrogen atoms can be look upon as bar magnets, in normal situations, they will flow inside...
A direct current in a set of windings creates a polar magnetic field. A torque acts on the rotor due to its relation to the external magnetic field. Just as the magnetic field of the rotor becomes fully aligned with the external magnetic field, the direction of the current in the windings on the armature reverses, thereby reversing the polarity of the rotor's electromagnetic field. A torque is once again exerted on the rotor, and it continues spinning.
Simply, the read and write head is a ferromagnetic core. It can produce a variety of magnetic fields through a variety of currents. to write data onto the media in ASC2.
T10.1b shows positive charges. In both cases the magnetic force is upward, just as the magnetic force on a conductor is the same whether the moving charges are positive or negative. In either case a moving charge is driven toward the upper edge of the strip by the magnetic force Fz = |q|vdB. If the charge carriers are electrons, an excess negative charge accumulates at the upper edge of the strip, leaving an excess positive charge at its lower edge. This accumulation continues until the resulting transverse electrostatic field E becomes large enough to cause a force (magnitude |q|E) that is equal and opposite to the magnetic force (magnitude |q|vd B). After that, there is no longer any net transverse force to deflect the moving charges. This electric field causes a transverse potential difference between opposite edges of the strip, called the Hall voltage or the Hall emf. The polarity depends on whether the moving charges are positive or negative. Experiments show that for metals the upper edge of the strip in Fig. T10.1a does become negatively charged, showing that the charge carriers in a metal are indeed negative
If the magnetic field is applied to a p-type semiconductor, the majority carriers (holes) and the minority carriers (free electrons) are pushed down towards bottom surface of the p-type semiconductor. In p-type semiconductor, free electrons are negligible. So the bottom surface of the p-type semiconductor is mostly accumulated with positive charge carriers (holes).
The fist computer, known as the abacus, was made of wood and parallel wires on which beads were strung. Arithmetic operations were performed when the beads were moved along the wire according to “programming” rules that had to be memorized by the user (Soma, 14). The second earliest computer, invented by Blaise Pascal in 1694, was a “digital calculating machine.” Pascal designed this first known digital computer to help his father, who was a tax collector. Pascal’s computer could only add numbers, and they had to be entered by turning dials (Soma, 32). It required a manual process like its ancestor, the abacus. Automation was introduced in the early 1800’s by a mathematics professor named Charles Babbage. He created an automatic calculation machine that was steam powered and stored up to 1000 50-digit numbers. Unlike its two earliest ancestors, Babbage’s invention was able to perform various operations. It relied on cards with holes punched in them, which are called “punch cards.” These cards carried out the programming and storing operations for the machine. Unluckily, Babbage’s creation flopped due to the lack of mechanical precision and the lack of demand for the product (Soma, 46). The machine could not operate efficiently because technology was t adequate to make the machine operate efficiently Computer interest dwindled for many years, and it wasn’t until the mid-1800’s that people became interested in them once again.
Before understanding the physics principles, one must understand the physical design that induces them. A magnetic disk is a flat, circular, rigid sheet of aluminum coated with a layer of magnetic material (can be double sided). The material usually is a form of iron oxide with various other elements added. The disk rotates upon a central axis and a movable read/write head writes information along concentric tracks (circular paths traced out by motion of the disk) on it. Multiple disks can be stacked to store more information. Typically (1985) 11 disks with 22 surfaces, of which 20 are used (minus top/bottom), are manipulated to read/write data.
The Earth’s magnetic field is a major component to exploring the earth. The north and the south poles have always been a guide for travelers. Using compasses, the direction of the north pole and the south pole has always been provided by the magnetic force of the magnetic field. What many people do not know though is the earth’s magnetic field provides way more than that. The magnetic field, also known as the magnetosphere, protects us from all kinds of harmful substances. Some of these substances include solar wind and harmful radiation from the sun. The magnetosphere also protects the atmosphere, which protects us.
The phenomenon called electromagnetic induction was first noticed and investigated by Michael Faraday, in 1831. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor and is a very important concept. Faraday discovered that, whenever the magnetic field about an electromagnet was made to grow and collapse by closing and opening the electric circuit of which it was a part, an electric current could be detected in a separate conductor nearby. Faraday also investigated the possibility that a current could be produced by a magnetic field being placed near a coiled wire. Just placing the magnet near the wire could not produce a current. Faraday discovered that a current could be produced in this situation only if the magnet had some velocity. The magnet could be moved in either a positive or negative direction but had to be in motion to produce any current in the wire. The current in the coil is called an induced current, because the current is brought about (or “induced”) by a changing magnetic field (Cutnell and Johnson 705). The induced current is sustained by an emf. Since a source of emf is always needed to produce a current, the coil itself behaves as if it were a source of emf. The emf is known as an induced emf. Thus, a changing magnetic field induces an emf in the coil, and the emf leads to an induced current (705). He also found that moving a conductor near a stationary permanent magnet caused a current to flow in the wire as long as it was moving as in the magnet and coiled wire set-up.
Everybody possesses some items that they want to keep, but rarely use. These items can take up space and become a hassle to store in your home. Using a storage facility is a great option to keep your possessions secure and easily accessible. Below are some crucial factors to help you know what to look for when choosing a self storage facility.
There are several different storage devices that can be used to store your data. These are the magnetic storage, optical storage, and solid state storage. According to Parsons and Oja (2014), “a magnetic storage devices stores the data by magnetizing microscopic particles on a disk or tape surface” (p
The research that established Faraday as the foremost experimental scientist of his day was, however, in the fields of electricity and magnetism. In 1821 he plotted the magnetic field around a conductor carrying an electric current; the existence of the magnetic field had first been observed by the Danish physicist Hans Christian Oersted in 1819.
that put large volumes of books and papers on CD-ROM. A single CD-ROM can hold
The mechanical energy (torque) is produced when opposing magnetic fields try to lineup. Therefore, the center line of the north pole of a magnetic field is directly opposite to the centerline of the south pole of another magnetic field (Fitzgerald et al., 1981). The opposing magnetic fields in a motor are generated by two separate concentrically oriented components, the stator and a rotor (Figure 2-5). Figure 2 5 Rotor and stator schematics of a three-phase DC motor. The stator is the stationary component, while the rotor is the rotational component of the motor.