Poynting Vector and Poynting Theorem PDF

Poynting vector and poynting theorem & The complex form of the Poynting vector Electromagnetics for medical physics ‫الكهرومغناطيسية للفيزياء الطبية‬ Second year ‫المستوى الثاني‬ Lectures Eleven and Twelve ‫المحاضرة الحادية عشر وال...

Poynting vector and poynting theorem & The complex form of the Poynting vector Electromagnetics for medical physics ‫الكهرومغناطيسية للفيزياء الطبية‬ Second year ‫المستوى الثاني‬ Lectures Eleven and Twelve ‫المحاضرة الحادية عشر والثانية عشر‬ Dr. Faten Monjed Hussein Poynting vector and poynting theorem When electromagnetic wave travels in space, it carries energy and energy density is always associated with electric fields and magnetic fields. The rate of energy travelled through per unit area i.e. the amount of energy flowing through per unit area in the perpendicular direction to the incident energy per unit time is called poynting vector. Mathematically poynting vector is represented as the direction of poynting vector is perpendicular to the plane containing 𝐸⃗ and 𝐻 ⃗ Poynting vector is also called as instantaneous energy flux density. Here rate of energy transfer 𝑃⃗ is perpendicular to both 𝐸⃗ and 𝐻 ⃗. Since it represents the rate of energy transfer per 2 unit area, its unit is W/m. Poynting theorem states that the net power flowing out of a given volume V is equal to the time rate of decrease of stored electromagnetic energy in that volume decreased by the conduction losses. i.e. total power leaving the volume = rate of decrease of stored electromagnetic energy – ohmic power dissipated due to motion of charge Proof : The energy density carried by the electromagnetic wave can be calculated using Maxwell's equations Complex Poynting’s Theorem