Derivation of Average Power Density by Poynting Theorem


Let’s say that average power density is denoted as (Savg)

We know that

wave velocity

=

Where integration of A is Equal to S (surface area),

where C is wave velocity and f is frequency.

calculating with help of energy density, then we can Write as

Poynting Theorem

The Poynting Theorem which was named After the British Physicist John Henry Poynting is a concept in electromagnetism that describes the energy inflow in an electromagnetic field. It Establishes a connection between the electromagnetic fields and the rate of energy transfer in a given region of space. Mathematically, it’s expressed as the cross-product of the electric field( E) and the magnetic field( H). It represents the power per unit area, or intensity, of the electromagnetic field. In this article, we will be Going Through The Poynting Theorem and its Mathematical Representations and Derive Some Equations.

Table of Content

  • What is the Poynting Theorem?
  • Mathematical Representation
  • Proof of Poynting Theorem
  • Derivation of Average power
  • Derivation of Average Power Density
  • Advantages and Disadvantages
  • Application
  • Solve Example


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What is the Poynting Theorem?

Poynting Theorem Explains How Electromagnetic Energy Travels Through Space. It Relates changes in Energy Density to the Poynting Vector, which indicates the direction and Amount of Energy transferred in the Electromagnetic fields....

Mathematical Representation

When electromagnetic waves travel in space, they transport energy. Energy density is linked to the electric and magnetic fields....

Proof of Poynting Theorem

Statement: At any point in a uniform plane wave, the cross product of electric field E and magnetic field H gives a measure of the rate of energy flow per unit area at that point....

Derivation of Average power by Poynting Theorem

Let us Derive Average Power by Poynting Theorem:...

Derivation of Average Power Density by Poynting Theorem

Let’s say that average power density is denoted as (Savg)...

Advantages and Disadvantages of Poynting Theorem

Given Below are List of Advantages and Disadvantages of Poynting Theorem:...

Application of Poynting Theorem

Wave propagation: Understanding the propagation of electromagnetic waves provides information about the direction and intensity of energy flow with the wave.Energy Conservation: The energy conservation principle in electromagnetic systems ensures that energy is neither created nor destroyed but only converted between different forms.Power transfer: This is used to determine the power transfer through a given area in an electromagnetic field.Radiation Pressure: It is used to determine radiation pressure, a force that can be harnessed in technologies such as optical tweezers....

Solve Example on Poynting Theorem

Q1. The Poynting vector of an electromagnetic wave in .What is the wavelength?...

Conclusion

Poynting Theoram is a important concept of electromagnetism and it can be defined as the Change in Electromagnetic Energy Density at a Point in a Space that will equal to the Negative of the Divergence of the Poynting Vector Minus the Power Dissipated as the Heat per Unit Volume. In this article, we have tried to cover the poynting theoram as well as its representation and proof. We have also discussed the two derivations related to puynting theorem and also discussed some examples on it. In simple words, Poynting theoram gives us understanding of transportation of electromagnetic energy and how it is converted in a given region of space....

FAQs on Poynting Theorem

1. What happens if the angle theta between E and B is zero or 180 degree ?...