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=MAGNETS= A piece of iron or other material which has its component atoms so ordered that the material exhibits properties of magnetism, such as attracting other iron-containing objects or aligning itself in an external magnetic field.

=TYPES OF MAGNETS=

Permanent Magnets
There are typically four categories of permanent magnets: neodymium iron boron (NdFeB), samarium cobalt (SmCo), alnico, and ceramic or ferrite magnets.

Neodymium Iron Boron (NdFeB) This type of magnet is composed of rare earth magnetic material, and has a high coercive force. They have an extremely high energy product range, up to 50 MGOe. Because of this high product energy level, they can usually be manufactured to be small and compact in size. However, NdFeB magnets have low mechanical strength, tend to be brittle, and low corrosion-resistance if left uncoated. If treated with gold, iron, or nickel plating, they can be used in many applications. They are very strong magnets and are difficult to demagnetize.

Samarium Cobalt (SmCo) Like NdFeB magnets, SmCo magnets are also very strong and difficult to demagnetize. They are also highly oxidation-resistant and temperature resistant, withstanding temperatures up to 300 degrees Celsius. Two different groups of SmCo magnets exist, divided based on their product energy range. The first series (Sm1Co5) has an energy product range of 15-22 MGOe. The second series (Sm2Co17) has a range that falls between 22 and 30 MGOe. However, they can be expensive and have low-mechanical strength.

Alnico Alnico magnets get their name from the first two letters of each of three main ingredients: aluminum, nickel, and cobalt. Although they feature good temperature resistance, they can easily be demagnetized and are sometimes replaced by ceramic and rare earth magnets in certain applications. They can be produced by either sintering or casting, with each process yielding different magnet characteristics. Sintering produces enhanced mechanical traits. Casting results in higher energy products and enables the magnets to achieve more complicated design features.

Ceramic or Ferrite Comprised of sintered iron oxide and barium or strontium carbonate, ceramic (or ferrite) magnets are typically inexpensive and easily produced, either through sintering or pressing. However, because these magnets tend to be brittle, they require grinding using a diamond wheel. They are one of the most commonly used types of magnet, and are strong and is not easy to demagnetize.

Temporary Magnets
Temporary magnets can vary in composition, as they are essentially any material that behaves like a permanent magnethttp://www.thomasnet.com/images/suppliers-small.png when in the presence of a magnetic field. Soft iron devices, such as paper clips, are often temporary magnets.

Electromagnets
Electromagnets are made by winding a wire into multiple loops around a core material—this formation is known as a solenoid. To magnetize electromagnets, an electrical current is passed through the solenoid to create a magnetic field. The field is strongest on the inside of the coil, and the strength of the field is proportionate to the number of loops and the strength of the current. The material at the center of the coil, the core of the solenoid, can also affect the strength of an electromagnet. If a wire is wrapped around a nonmagnetic material, such as a piece of wood, the overall magnetic field will not be very strong. However, if the core is composed of ferromagnetic material, such as iron, the strength of the magnet will dramatically increase.

=HOW DO MAGNETS WORK=

Understanding how magnets work means figuring out the dynamics of a magnetic field. Consider the space that surrounds a magnet. This space is occupied by a magnetic force and is called a magnetic field. If a magnet is placed within this field, it will be acted upon by magnetic forces. A magnetic field is created as the result of moving charges. A good example of this is electric current that flows through a wire. When this occurs, there are negatively charged, subatomic particles, called electrons, moving through the wire. As these charges move, a magnetic field forms around the wire. Likewise, the magnetic field of a magnet is created by the movement of electrons. A magnet’s magnetic field either attracts or repels certain metals, as well as other magnets. A magnet has two ends that are referred to as poles. One pole is called north and the other one is referred to as south. To attract magnets to each other, you have to place opposite ends of two magnets near each other. Placing like ends of two magnets near each other causes the opposite to occur; the two magnets repel each other. Interestingly, the Earth has a natural, magnetic field at is core. If you take a look at a compass, you will notice that one side is marked “N” and faces toward the Earth’s northern magnetic pole. As such, this part of the compass is referred to as the North-seeking pole. However, the Earth’s north magnetic pole should not be confused with its North Pole. The North Pole is located hundreds of miles away from the north-seeking pole.

= PROPERTIES =


 * All the magnets have two types of poles: north-seeking poles or north poles and south-seeking poles or south poles.
 * The magnetic strength is the strongest at the poles of the magnet.
 * When you freely suspend a bar magnet in a horizontal position, the magnetic field of the bar magnet will interact with the magnetic field of the Earth. This will cause the bar magnet to come to rest in a north-south direction, where the north pole of the magnet points to the north pole of the Earth.
 * Like poles repel and unlike poles attract. (just as like charges repel and unlike charges attract).
 * Magnets attract magnetic materials such as iron, steel, cobalt and nickel.
 * The stronger a magnet, the larger will be the attractive or repulsive force between other magnets.
 * The closer together the two magnets are, the greater is the magnetic force between them.

=APPLICATIONS=

Within the industrial sector, magnets are often used as magnetic sweepers, sorters, and to separate impure metals during metal manufacturing or recycling. In electronic applications, magnets are used in speakers, televisions, telephones, radios, and videotapes. Typically, electromagnets are used within televisions, computers, and telephones because of their extreme strength. For this same reason, they are also used in on-off applications, such as cranes sued for heavy lifting. Permanent magnets are perhaps the most common type—they are used to manufacture refrigerator magnets, as well as in jewelry making. Temporary magnets can be useful in applications that generate a temporary magnetic field and require a magnetic response for the duration of the field.

Common uses
Magnets have their lot of applications in the daily life. The major 10 uses of the magnets are as follows:


 * 1)  They are used to construct the electrical motors and the generators which convert the electrical energy into mechanical energy and vice verse.
 * 2) They are also used in the speakers which can convert the electrical energy into sound energy.
 * 3) They are used in the electrical bells.
 * 4) They are used in the Maglev trains. In the Maglev trains, the super conducting magnets are used on the tracks on which the train floats. These types of the trains are working on the repulsion force of the magnets.
 * 5) They are also used to sort out the magnetic and non magnetic substances from the scrap.
 * 6) They are used in TV screens, computer screens, telephones and in tape recorders.
 * 7) They are used by the candy or cold drink vendors to separate the metallic cap from the lots.
 * 8) They are used in cranes.
 * 9) They are used in the refrigerators to keep the door close.
 * 10) The most important use of the magnet is the magnetic compass which is used to find the geographical directions.

=REFRENCE= Thosmasnet.com, www.miniphysics.com, www.meriam-webster.com