Pre-Quantum Electrodynamics

Momentum emd.ce.mom

  • Gr 8.2.3

From Newton's second law, F=dpmechdt we have dpmechdt=ε0μ0ddtVSdτ+STda in which the first integral can be interpreted as the momentum stored in the EM fields, and the second is the momentum per unit time flowing in through the surface.

This is thus simply a conservation law for momentum, with

Momentum density in the EM fields

(gExB)g=ε0μ0S=ε0E×B

In a region in which the mechanical momentum is not changing due to external influences, we then have the

Continuity equation for EM momentum

(contg)tgT=0




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Author: Jean-Sébastien Caux

Created: 2024-02-27 Tue 10:31