Question

What are permanent magnets? What is an efficient way of preparing a permanent magnet? Write two characteristic properties of materials which are required to select them for making permanent magnets.

Answer 1

Hint: Magnets are a type of materials which tend to have magnetizing properties. They create a magnetic field around themselves which is felt by those substances which are ferromagnetic in nature like iron, steel and others. Here, we will understand about permanent magnets, their method of preparation and the properties of metal which are required to be a magnetic material.

Complete answer:
Magnets are generally of two types namely permanent magnets and electromagnets.
Permanent magnets: The magnets which do not lose their magnetic property under the influence of any other external agency are known as permanent magnets. Their magnetic property does not lose with time hence are known as permanent.

In order to make a permanent magnet efficiently, we have to put a ferromagnetic material inside a solenoid and pass electric currents through it. In this way we can make a permanent magnet of high standards. Two characteristic properties of any material which are mandatory for making permanent magnets are as follows:
(i) It must have high retentivity so that it exerts a strong magnetic field around itself.
(ii) There must be high coercivity so that the magnetization of the material does not get wiped out by strong external fields, mechanical issues and changing temperature.

Note: Retentivity refers to the ability of a substance or material to withstand a magnetic field even when an external magnetic field is being removed. Coercivity refers to the minimum value of intensity of magnetization that would bring the substance used as a magnet to convert into its original state.