The above equation is obviously a bit complicated, so to simplify things a bit, we introduce the Poynting vector . Definition − “Poynting vector gives the rate of energy transfer per unit area” This vector describes the energy per unit time, per unit area, transported by the field - in other words, it is the energy flux density. Define the Poynting vector. The direction of P is perpendicular to E and H and in the direction of vector E x H. Proof.

Poynting vector describes the energy of the EM Wave per unit time per unit area at any given instant of time.

John Henry Poynting first derived this vector in 1884 and hence it was named after him. Derivation and Explanation of the Poynting Theorem The Poynting Theorem is in the nature of a statement of the conservation of energy for a configuration consisting of electric and magnetic fields acting on charges. Poynting. Consider Maxwell’s fourth equation (Modified Ampere’s Circuital Law), that is del x H = J + ε dE/dt Here P → Poynting vector and it is named after its discoverer, J.H.