3.3 Conservation of linear momentum & Maxwell Stress Tensor
3.3.1 Derivation and definition of Maxwell Stress Tensor
Maxwell Stress Tensor
symmetric:
define:
electromechanic momentum density
with surface normal
Lec 09  21. Jan
Thursday, January 22, 2009
9:45 PM
Lecture Notes
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3.3.2 Force laws
local representation of conservation law
Poynting
vector
force density
momentum density
Integrated form:
force on area G
Force law now expressed exclusively in terms of fields:

external field

internal fields due to charges & currents in volume G
represents force per unit area acting on surface
force on surface element
(vector character!)
3.3.3: Example (Calculation details see Griffith, example 8.2, p. 353)
Q: total charge
R: radius of sphere
uniformly charged sphere
Total force acting on upper part of
sphere ("northern hemisphere")?