Greeks used the term magnet in six hundred B.C. for the mysterious stone that seemed to attract iron and other materials. Today a variety of magnets of all shapes and sizes, made of materials ranging from ceramic (strontium ferrite), alnico, rare earth and flexible and rubber-like material is found.

A magnet can be defined as a simple material that possesses a magnetic field. This magnetic field is a magnetic effect of magnetic materials. At any given point the magnetic field is stated by magnitude and direction. A permanent magnet creates its own continual magnetic field has it is a material that is magnetized. For instance refrigerator magnet.The electromagnet is defined as a tightly wound helical coil of wire which is usually found with an iron core. Temporary magnets are those magnets which act like a permanent magnet while they are within a strong magnetic field.

One fascinating fact about the magnet is that they do not move. But the charges inside them are moving. Inside a metal, the electrons of each atom are orbiting the nucleus of that atom. And when charges move, they produce magnetic fields. But in non-magnetic materials, there are electrons orbiting in both directions, and their magnetic fields cancel each other out. The overall magnetic field generated is zero.

Magnets have wide applications. A compass is a magnetic device which has used to guide people about the directions. In fact, the compass was most probably the first important magnetic device discovered. This discovery had helped Mariners who often had trouble in navigation when the clouds covered the sun or stars. Magnets are also used to in homes to organize kitchen utensils and as planning magnetic boards to display charts. Magnets play a role in lifting, retrieving and so on.

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Practise This Question

An equilateral triangular loop of side l carries a current I. It is placed in a magnetic field B such that the plane of the loop is in the direction of B. The torque on the loop is