What is Magnet:- About some method of making an iron rod or piece of magnet, there
are three ways to make it. So let’s see what is magnet and radiation
(1) Touch method
(2) By means of electric current
(3) Induction method
This method is also divided as follows.
(a)Single touch method
(b) Double touch method
(c)divided touch method
(a) One touch method:
In this method, the steel bar which is to be made a magnet is rubbed with one pole of a magnet in the same direction in such a way that the other pole is away. Repeat this method several times to bring the rod into a magnetized form.
(b) Dual Touch Method :
In this method, the bar which has to be magnetized is placed between the two opposite poles of the magnet and the rubbing magnets are placed between the rods in such a way that a small piece of wood is lying between them. Should not be lifted from the surface. Then they are rubbed from one end to the other and finally stop rubbing from where they started rubbing.
(c) Divided touch method:
Here also two different poles of rubbing magnets are held as described earlier. They are then separated from opposite ends of the surface of the steel bar. The rubbing magnets are then lifted off the surface of the steel rod. And then bring it in the middle of the rod. Repeat this process again and again. In this way the steel rod becomes a permanent magnet. But its power is very less.
By electric current
In this method, the insulated copper wire is wrapped over the rod to be made of magnet and then for some time excess current (DC) from the battery is passed through the wire and the steel bar then becomes more magnetized. If the rod is of soft iron Then the magnetic property will remain in it till the current flows, but its magnetic property almost ends as soon as the flow of current is stopped. Magnets made in this way are called electromagnets and are mainly used in the laboratory.
Induction method The commercial method of making this permanent magnet is to use a pole charger, which consists of a high-tonnage coil andan iron core inside.
The piece of steel to be made magnet is placed on the iron core lying inside the coil and then direct current is passed through the coil. Now the iron core becomes a powerful magnet and thus the piece of steel placed on it It also becomes a magnet by induction. After turning off the current, the magnetized steel piece is lifted.
This method has the following properties:1. In this method even small pieces of steel can be easily magnetized.2. It takes very less time to make magnets.3. Steel pieces of any size can be easily magnetized.
This is a commercial method of making permanent magnets for speakers, telephones, microphones, earphones, electric instruments, etc.
Radiation is the process of heat transfer in which heat moves directly from a hotter body to a colder body. In this process a medium is not required between the two bodies. And even if there is a medium, it is not affected and the heat It does not heat it. The heat transmitted by radiation from the Sun to the Earth is called radiative heat. This heat is also called heat radiation.
To understand heat transfer by radiation, it is assumed that every object emits energy continuously at all times. This energy is called radiative energy or thermal radiation. It is in the form of electromagnetic waves. Waves light travels at the speed of light and they propagate through vacuum or any medium such as air. When these waves fall on an object which is not transparent to them, they are absorbed and their energy is converted into heat It becomes. The thermal radiation (thermal radiation) emitted by a body depends on time and per unit surface area, the nature of its surface and its temperature. The rate of emission is low at low temperature. The emission rate is the fourth quadrant of the temperature as the temperature is increased. starts increasing in proportion to T⁴.
Properties of radiation energy Thermal radiation travels in a vacuum with the velocity of light in a straight line. It obeys the law of inverse square. It reflects and refracts like light. Exerts a small but finite pressure on the surface on which it falls