Poynting Vector: "S Points Radially Inward" Explained

In summary, the Poynting vector, which represents a flow of electromagnetic energy, points inwards towards the center of a charged capacitor as it is storing energy in the form of an electrical field. This may seem unusual, but it is a common characteristic of the Poynting vector and makes sense in the context of charging and discharging a capacitor. When the capacitor is in a stable state, the Poynting vector will be null.
  • #1
yannick^
2
0
I have a question about the Poynting vector:

mit.edu/8.02t/www/materials/StudyGuide/guide13.pdf (page 44/51)

What is the physical interpretation of "S points radially inward". That seems kinda weird. Energy flows to the center?

cheers
 
Physics news on Phys.org
  • #2
Couldn't find your exact page on the link...but yes, seems unusual but that is typical for Poynting vector...say, of a coil or capacitor being charged...the energy flows orthogonally into it from the surrounding space otside the coil.

Creator
 
Last edited:
  • #3
Yes.

It's not so weird after all: while being charged, the capacitor is storing energy in the form of the electrical field which is being "built" in the dielectric material inside it. Since the Poynting vector represents a flow of electromagnetic energy, it makes sense that during charging it will point towards the inside of the capacitor, and during discharging it will point outwards. In a stable condition of the capacitor, the Poyting vector will be null.
 

What is the Poynting Vector?

The Poynting Vector is a mathematical tool used to describe the direction and magnitude of electromagnetic energy flow in a given area. It is denoted by the symbol S and is measured in watts per square meter.

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. It is also influenced by the permittivity and permeability of the medium in which the electromagnetic energy is propagating.

What does it mean when the Poynting Vector points radially inward?

When the Poynting Vector points radially inward at a given point, it indicates that electromagnetic energy is being absorbed or dissipated at that point. This is often seen in materials with high resistivity, such as metals.

Why is the Poynting Vector important?

The Poynting Vector is important because it provides valuable information about the direction and intensity of electromagnetic energy flow. This is crucial in understanding and analyzing various electromagnetic phenomena, such as radiation, refraction, and reflection.

How does the Poynting Vector relate to the electromagnetic wave equation?

The Poynting Vector is directly related to the electromagnetic wave equation, which describes the propagation of electromagnetic waves through a medium. It is a key component in the derivation of the wave equation and plays a crucial role in understanding the behavior of electromagnetic waves.

Similar threads

Replies
10
Views
5K
Replies
14
Views
962
Replies
1
Views
1K
  • Classical Physics
Replies
6
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
1K
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Advanced Physics Homework Help
2
Replies
39
Views
10K
Replies
4
Views
1K
  • Advanced Physics Homework Help
Replies
2
Views
1K
Back
Top