Magnetic field:

A magnetic field is a field of force produced by the magnetic object or particle, or by a changing the electrical field and can be detected by the force it exerts on the other magnetic materials and moving electric charges. The magnetic field at any given point can be specified by a direction and a magnitude both (or strength); as such it is a vector field. A magnetic field can be created by moving charges, like a current-carrying wire. A magnetic field can be created by spin magnetic dipole moment, and by orbital magnetic dipole moment of an electron within an atom.

Objects which produce the magnetic field of own are called magnets. Magnets exert torques and forces on each other through the magnetic fields they create. Magnets tend to align in the direction of the local magnetic field. Compasses use this effect to measure the direction of the

 local magnetic field, produced by the Earth. Electrical currents and moving electrical charges generate the magnetic fields. Even the magnetic field of the magnetic material can be modeled as being because of moving electrical charges. Magnetic fields exert forces on moving the electrical charges.

Magnetic fields have had a number of uses in ancient and modern society. Rotating magnetic fields are utilized in electrical motors and generators both. Magnetic forces give information about the charge carriers in the material through the Hall Effect. The interaction of magnetic fields in the electrical devices like transformers is studied in discipline of magnetic circuits.

The B-field depends on currents only. While H depends on macroscopic currents and a factor which is closely related to the concept of magnetic charge. The B-field is defined in many equivalent ways based on the effects it has on its environment. For example, a particle having an electric charge, q,

And moving in a B-field with a velocity, v, experiences a force, F, called as Lorentz force. In SI units, Lorentz force equation can be given by

F=BQV

In materials for which M is proportional to B, relationship between B and H can be cast into simpler form: H = B/µ, where µ is a material dependent parameter called as permeability. In the free space, there is no magnetization, M, such that H = B/µ0. For many materials, there is no simple relationship between B and M. For instance, ferromagnetic materials and superconductors have a magnetization which is a multiple-valued function of B because of hysteresis.