Impulse of electromagnetic field

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The discussion focuses on the relationship between the mechanical impulse of particles in an electromagnetic field and the conservation of impulse. The equation \(\int_V\vec{g}dV=\vec{const}\) is identified as a necessary but not always sufficient condition for the law of action and reaction in electrodynamics. Participants debate the conditions under which this equation holds true and its implications for Newton's Third Law. There is a call for clarification on the specific scenarios where this relationship is valid. The conversation highlights the complexities of applying classical mechanics principles to electromagnetic contexts.
Petar Mali
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We have

\vec{F}=\int_V\vec{f}dV=-\frac{d}{dt}\int_V(\vec{D}\times \vec{B})dV

\vec{g}=\vec{D}\times \vec{B}

\vec{F}=-\frac{d}{dt}\int_V\vec{g}dV

\vec{F}=\frac{d\vec{p}_{mech}}{dt}

\frac{d}{dt}(\vec{p}_{mech}+\int_V\vec{g}dV)=0

\vec{p}_{mech}+\int_V\vec{g}dV=\vec{const}

In total field law of conservation of impulse

\vec{p}_{mech} - mechanical impulse of particles in field

In one book I found that \int_V\vec{g}dV=\vec{const} is necessary but not always sufficient condition for law of action and reaction in electrodynamics.

My question is when is \int_V\vec{g}dV=\vec{const} necessary and sufficient condition for this law? Thanks for your answer!
 
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Does anyone know this?
 
Petar Mali said:
\vec{p}_{mech}+\int_V\vec{g}dV=\vec{const}

In total field law of conservation of impulse

\vec{p}_{mech} - mechanical impulse of particles in field

In one book I found that \int_V\vec{g}dV=\vec{const} is necessary but not always sufficient condition for law of action and reaction in electrodynamics.

My question is when is \int_V\vec{g}dV=\vec{const} necessary and sufficient condition for this law? Thanks for your answer!

If you believe
\vec{p}_{mech}+\int_V\vec{g}dV=\vec{const},
then isn't the answer obviously, yes?
I assume you mean NIII for the forces on objects.
 
NIII?

No! It's not obviously, I think. What is your idea?
 
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