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In physics, the Maxwell stress tensor is the stress tensor of an electromagnetic field. In cgs units, it is given by: Image File history File links Broom_icon. ... Image File history File links Broom_icon. ... This is a discussion of a present category of science. ... This article is in need of attention from an expert on the subject. ... The electromagnetic field is a physical field that is produced by electrically charged objects and which affects the behaviour of charged objects in the vicinity of the field. ...

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where E is the electric field, H is the magnetic field and δ is Kronecker's delta. In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... In mathematics, the Kronecker delta or Kroneckers delta, named after Leopold Kronecker (1823-1891), is a function of two variables, usually integers, which is 1 if they are equal, and 0 otherwise. ...

In SI units, it is given by:

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where and μ₀ are the permittivity and permeability of vacuum respectively. Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ... In electromagnetism, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. ...

The element ij of the Maxwell stress tensor has units of momentum per unit of area and unit of time and gives the flux of momentum parallel to the ith axis crossing a surface normal to the jth axis per unit of time.

These units can also be seen as units of force per unit of area (pressure), and the ij element of the tensor can also be interpreted as the force parallel to the ith axis suffered by a surface normal to the jth axis per unit of area. Indeed the diagonal elements give the pressure acting on a differential area element normal to the corresponding axis. Unlike forces due to the pressure of an ideal gas, an area element in the electromagnetic field also feels a force in a direction that is not normal to the element. This shear (rather than pressure) is given by the off-diagonal elements of the stress tensor.

See also

• Energy density of electric and magnetic fields
• Poynting vector
• Electromagnetic stress-energy tensor

Energy density is the amount of energy stored in a given system or region of space per unit volume or per unit mass, depending on the context. ... The Poynting vector describes the energy flux (J·m−2·s−1) of an electromagnetic field. ... In physics, the electromagnetic stress-energy tensor is the portion of the stress-energy tensor due to the electromagnetic field. ...

References

• Richard Becker,"Electromagnetic Fields and Interactions",Dover Publications Inc.,1964