Magnetism - Basic concepts:
1. Pole strength: The ability of a pole of a magnet to attract or repel another magnetic pole is called its pole strength. Units : A-m
2. Magnetic Permeability : Magnetic Permeability ( m ) of a medium is defined as its ability to allow the magnetic lines of force to pass through it or to allow itself to be influenced by magnetic field.
Units : Henry/meter.
3. Relative Permeability :The ratio of the permeability of a medium to the permeability of free space is defined as 'relative permeability' ( m r ). Relative permeability is a ratio, it has no units.
4. Unit magnetic pole : The unit magnetic pole is defined as that pole which repels an identical pole at 1 meter distance with a force of 10^{-7} N.
5. Magnetic field induction (or) Magnetic flux density : Magnetic field induction or magnetic flux density is defined as the magnetic flux passing through a unit normal area = weber/(meter)^{2}. = tesla
6. Magnetic field induction due to a magnet at point
The magnetic field induction due to a magnet at a point is defined as the force acting on a unit north pole placed at the point. Units : N/A - m
7. Intensity of magnetic field: The intensity of a magnetic field (H) at a point is defined as the force acting on a unit north pole placed at the point, independent of the medium. Units: A/ m
8. Magnetic Moment (M): Magnetic moment (m) of a bar magnet is measured by the product of its pole strength (m) and its magnetic length.