Poynting vector

The electromagnetic energy-flux density vector, defined as the cross product of electric and magnetic fields. Its direction gives energy flow, and its magnitude gives power crossing a unit area.

Poynting theorem: An energy-conservation law relating electromagnetic energy flow, stored field energy, and work done on charges. It derives the local balance law whose flow term is the Poynting vector.
Electric field: A vector field describing the electric force per unit charge at each point. It supplies one of the two fields in the defining cross product.
Time-averaged Poynting vector: The average electromagnetic energy-flux density over time, commonly used for sinusoidal fields. It gives steady power flow when instantaneous fields oscillate too rapidly to track.
Lorentz force: The force exerted on a charged particle by electric and magnetic fields. It describes energy transfer to charged matter, while the vector describes field-energy flow.
Maxwell's equations: The equations governing how electric and magnetic fields are produced and change. They yield the conservation equation that defines electromagnetic energy flux.
Magnetic field: A field describing magnetic influence and the forces it produces on moving charges and magnetic materials. Its orientation relative to the electric field determines the energy-flow direction.
Antenna radiation: The emission of electromagnetic waves by an antenna into its surroundings. Integrating outward energy flux over a surface gives an antenna's radiated power.
Electromagnetic momentum density: The momentum carried per unit volume by an electromagnetic field. It is related to energy flux but represents momentum, not power crossing area.
Electromagnetic energy density: The energy stored per unit volume in electric and magnetic fields. Together with the Poynting vector, it appears in local electromagnetic energy conservation.
Cross product: A vector operation that produces a vector perpendicular to two input vectors, with magnitude tied to their angle. It explains why energy flow is perpendicular to both electromagnetic fields.

Linked from 8 pages