Magnetic retentivity And terms

What is Retentivity of a magnet-

Even after removing the magnetizing force that magnetizes a magnetic material, there is some magnetism left in that substance, which is called Residual Magnetism. The property of the substance that causes it to hold residual magnetism is called Retentiivity. The material is selected on the basis of the retentiivity power to form the magnet. The retentiivity strength of the iron is higher than the soft iron.

What Use Of Magnetic Needle -

In a magnetic needle or magnetic compass, a small needle-shaped magnet is mounted on a pivot in a shell made of non-magnetic material with a glass lid. The northern-most portion of the needle is painted black. So that the northern pole can be clearly identified from both the poles. According to the properties described above, the magnetic needle always stays in the north-south direction. This miniature machine is used in laboratories. Sailors, with the help of this device, use the top of their vessel to set the direction in the voluntary direction rather than the true north.

Magnetic Terms-

Magnetic Pole - 

The edge of the magnet where it has the most power.

Magnetic Line of force - 

Magnetic lines that move south to north inside a magnet bar and north to south outside the magnet bar are called magnetic lines of force.

Magnetic Flux - 

The total magnetic lines that emerge from the pole of a magnet are called Magnetic Flux. It is denoted by ɸ. Its unit is Weber or Maxwell and is represented by Wb.
                           Or where the magnetic line goes in or out is called Magnetic Pole.
                           Or the edge of the magnet where there are more magnetic lines of force.

Magnetic Axis- 

The imaginary straight line joining the two poles of a bar magnet is called Magnetic Axis.

1Weber = 10⁸Maxwell
 or
1Weber = 10⁸lines

Magnetic Flux Density - 

Magnetic lines passing through a vertical per unit area of ​​a substance are called magnetic flux density. It is represented by B, its unit is web / square meter or tesla and it is represented by Wb / m².

B = ɸ / a

Here -
B = Magnetic flux density in Wb / m²

ɸ = Magnetic flux in Wb
a = Area of ​​vertical plane of magnetic force line in m²

Magnetic Field - 

The area around the magnet as far as the effect of the magnetic lines is called the magnetic field.

Magneto Motive Force (MMF) - 

This is a type of force that accelerates the magnetic flux in magnetic circuits. It is written in short form MMF. It is denoted by Fm. Its unit is ampere turn (A-T).Fm = N I
Here-
Fm = Magneto Motive Force, A-T
N = Number of turns in the coil
I = Electric current, in ampere

Magnetic Field Strength- 

The magnetic force exerted on a unit pole placed at a point in a magnetic field is called magnetic field strength. It is denoted by H. Its unit is ampere turn / meter (AT / m).H = Fm / l
(Fm = NI)
H = NI / l

Here-
H = Magnetic field intensity, A-T / m
Fm = Magneto Motive Force, A-T

N = Number of turns in the coil

I = Electric current, in ampere
l = Length of the coil, in meters