MOTION MOUNTAIN

liquid electricity, invisible fields and maximum speed 73
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A summary: three basic facts about electricity
The experiments we have described so far show three basic results:
⊳ Electric charges exert forces on other charges.
⊳ Electric charges are conserved.
⊳ Charges, like all matter, move slower than light.
From these three statements – the definition of charge, the conservation of charge, and
the invariance of the speed of light – we can deduce every aspect of classical electrodynamics.In
particular, theLagrangian ofelectrodynamicsandMaxwell’s fieldequations
canbededucedfromthesethreestatements;theydescribethewaythatchargesproduce
any electric, magnetic or electromagnetic field. Also the Lorentz force can be deduced;
it describes how the motion of massive charges and the motion of the electromagnetic
field is related.
The proof of the connection between charge conservation and the field equations can
be given mathematically; we do not present it here, because the algebra is somewhat
involved. The essential connection to remember is: all of electrodynamics follows from
the properties of charges that we have discovered so far.
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net