Continuum mechanical analogous of Maxwell stress tensor

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SUMMARY

The discussion centers on the analogy between the Maxwell stress tensor in electromagnetism and the stress tensor in continuum mechanics. The Maxwell stress tensor, denoted as ##\bar{\bar{\mathbf{T}}}##, is used to calculate the total force ##\mathbf{f}## acting on a system of charges within a volume bounded by surface ##S##. This relationship is formally analogous to the stress tensor in continuum mechanics, which also determines the forces acting on a system of masses. The key takeaway is that the Maxwell stress tensor serves as the stress tensor for the electromagnetic field, while the stress tensor in mechanics is used for mechanical systems.

PREREQUISITES
  • Understanding of Maxwell stress tensor in electromagnetism
  • Familiarity with continuum mechanics principles
  • Knowledge of stress tensor concepts in mechanics
  • Basic grasp of the relationship between forces and momentum in physical systems
NEXT STEPS
  • Study the derivation and applications of the Maxwell stress tensor in electromagnetism
  • Explore the properties and applications of the stress tensor in continuum mechanics
  • Investigate the relationship between mechanical momentum and forces in physical systems
  • Learn about the stress-energy tensor and its implications in both mechanics and electromagnetism
USEFUL FOR

This discussion is beneficial for physicists, engineers, and students studying electromagnetism and continuum mechanics, particularly those interested in the mathematical relationships between forces and tensors in physical systems.

crick
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Maxwell stress tensor ##\bar{\bar{\mathbf{T}}}## in the static case can be used to determine the total force ##\mathbf{f}## acting on a system of charges contanined in the volume bounded by ##S##

$$ \int_{S} \bar{\bar{\mathbf{T}}} \cdot \mathbf n \,\,d S=\mathbf{f}= \frac{d}{dt} \mathbf {{Q_{mech}}}\tag{1}$$

Where ## \mathbf {{Q_{mech}}}## is the (mechanical) momentum of the system of charges.

What theorem/relation is formally analogous to ##(1)## in continuum mechanics? I've read that also in continuum mechanic one can introduce a tensor such that the value of its components on a surface ##S## enclosing a system of masses determines the forces acting on the masses completely.

I could not find this analogy on Jackson or Griffiths, so what is the tensor that is similar to Maxwell stress tensor in mechanics? Is it the stress tensor? By which theorem does it determine the forces on a system of masses?
 
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crick said:
Is it the stress tensor?
Partially, the stress tensor is the spatial-spatial part. The stress energy tensor also incorporates the momentum and energy densities.

Edit: So forget that. You were only asking about the 3D case, not the spacetime 4D case. It is just the stress tensor. The Maxwell stress tensor is the stress tensor of a continuum - the EM field.
 

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