# Magnetic Flux

The total number of magnetic lines of force of a magnet is called magnetic flux. It is represented by phi (ϕ) and its unit is Weber.

## MAGNETIC FLUX DENSITY

Magnetic flux per unit area is called magnetic flux density. It is given as B = ϕ/A.

Where "B" is the magnetic flux density, (ϕ) is the magnetic flux and "A" is the area. The unit of magnetic flux density is Weber/m2.it is also called tesla.

## MAGNETIZING FORCE

When current is passed through a coil having length of m, meter and N, turn then the magnetizing force is given by the fallowing formula

H = NI / L A/m

Where "H" number of turns, "I" current "L" length of coil. Its unit is A/m.

## ABSOLUTE AND RELATIVE PERMEABILITY OF A MEDIUM

The phenomena of magnetism and electro magnetism are dependent upon a certain property of the medium called its permeability. Every medium is supposed to posse's two permeability.

### ABSOLUTE AND RELATIVE PERMEABILITY

For measuring relative permeability, vacuum or free space is chosen as the reference medium. It is allotted an absolute permeability of υ0 = 4π x 10-7 H/m. absolutely, relative permeability of vacuum with reference to its self-only. Hence, for free space,

Absolute permeability = υ0 = 4π x 10-7 H/m

Relative permeability = υ0 = 1

Now take other medium than vacuum. If its relative permeability, as compared to vacuum is υr, then its absolutes permeability is

υ = υ0 υr H/m

## MAGNETIC FIELD DUE TO CURRENT IN STRAIGHT CONDUCTOR

When a current flows through a conductor, magnetic lines of force are set up which surround the conductor. If the conductor is a straight wire the magnetic lines of force are in the form of concentric circle around the wire. As shown in the fig