Electromagnetism - Poynting vector

In summary, the Poynting vector at a specific point, p, represents the energy flowing out of that point per unit time and unit of cross sectional area. This vector is also proportional to the momentum density of the field, meaning it has the same direction as the energy flow. Additional information can be added if needed.
  • #1
Kontilera
179
24
Hello!
I' currently reading EM and am in need of a verification that I understood it correctly before proceeding. Just to see if I got this right:

The energy flowing out of a point, p, is described by the Poynting vector of the field at that point. The momentum density of the field is proportional to the Poyinting vector and therefore proportional to (i.e. has the same direction as) the energy flow from that point.

Please comment on this if you feel that I'm missing something or important information easily can be added.

Best Regards and Merry Christmas
Kontilera
 
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  • #2
The energy flowing out of a point, p, is described by the Poynting vector of the field at that point
You may want to sharpen that as:
"Poynting vector is the amount of energy flowing at the point of its evaluation per unit time and per unit of cross sectional area transverse to its direction."
 

1. What is the Poynting vector?

The Poynting vector is a mathematical concept used in electromagnetism to describe the direction and magnitude of electromagnetic energy flow in a given region of space. It is named after its discoverer, John Henry Poynting.

2. How is the Poynting vector calculated?

The Poynting vector is calculated by taking the cross product of the electric field vector and the magnetic field vector at a given point in space. This results in a vector that represents the direction and magnitude of the energy flow at that point.

3. What is the significance of the Poynting vector?

The Poynting vector is significant because it helps us understand and quantify the transfer of energy through electromagnetic fields. It is used in many practical applications, such as in the design of antennas and power transmission systems.

4. How does the Poynting vector relate to electromagnetic waves?

The Poynting vector is directly related to electromagnetic waves. It represents the direction and magnitude of the energy flow of these waves, which are a combination of electric and magnetic fields oscillating at right angles to each other.

5. Can the Poynting vector be negative?

Yes, the Poynting vector can be negative. This indicates that the energy flow is in the opposite direction of the vector. In other words, energy is being absorbed rather than radiated. This is commonly seen in materials with high absorption coefficients, such as metals.

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