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Home > Basic Electronics Concept > Magnetism
Magnetism

Magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials.

Unlike electric charges (such as those observed when amber is rubbed against cloth), magnetic objects possessed two poles of opposite effect, denoted "north" and "south" after their self-orientation to the earth.

Materials like iron, steel, and the mineral lodestone are influenced by the presence of a magnetic field.

Basically, a magnetic field arises due to the moving electric charges.

There are various types of magnets depending upon Orientation of Electric Charges.

  • Magnetic Poles
    When a magnet is suspended freely, one side points North. This is called the North Pole of the magnet. The other side points South, and is called the South Pole of the magnet.

    A magnetic compass is used for finding north and South Pole.

  • Magnetic Fields
    A magnet is surrounded by an invisible force field. Electric coils, currents in wires, and permanent magnets are all sources of magnetic field. Moving charged particles produces magnetic fields. In case of electromagnets, electron flow through a coil of wire connected to a battery; in permanent magnets, spinning electrons within the atoms produces the field. Lines of magnetic force can be seen around a magnet by sprinkling iron filings on to a sheet above it and tapping the sheet. The strength of the magnetic force is strongest close to the poles and gets weaker as you move away from the poles.

  • Magnetic DomainsMagnetic Domains
    Normally the electrons are paired up and they cancel each others field; but in iron, some of the electrons are unpaired. Their spins tend to line up together, creating tiny pockets of magnetism called magnetic In the atoms of magnetic metals, the electrons spinning around the nucleus create a small magnetic field. domains.

Therefore, in magnetized material, magnetic domains are oriented towards one direction but in unmagnetised material, magnetic domains are randomly oriented in different directions.

Depending upon domains Magnets are classified in three categories, which are as follows
1. Permanent Magnets
2. Temporary Magnets
3. Electro Magnets

1. Permanent Magnets
Permanent magnets are made from a ferromagnetic material, which at some point of time has been exposed, to a magnetic field. They are permanent in the sense that once they are magnetized, they retain a level of magnetism. Consider ferromagnetic material (one that can be magnetized without much effort), which can be made into a magnet by placing it in the centre of an electric coil or solenoid and passing a large current through the coil. If the material is magnetically `hard, it will retain its magnetism even when the current has been switched off. Permanent magnets are made from such hard materials as steel, nickel, and cobalt. Such magnetic alloys are used in electrical equipment and electronic devices

2. Temporary Magnets
Temporary magnets are those which act like a permanent magnet when they are within a strong magnetic field, but lose their magnetic property when the magnetic field disappears.

Examples: paperclips and nails and other soft iron items.

3. Electro Magnets
An electromagnet is a tightly wound helical coil of wire, usually with an iron core, which acts like a permanent magnet when current is flowing in the wire. The strength and polarity of the magnetic field produced by the electromagnet are adjustable by changing the magnitude of the current flowing through the wire and by changing the direction of the current flow.

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