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Where
is the missing energy ?
A capacitor (capacity C) is charged at the voltage U
and then disconnected from the power supply. It
contains the electric charge Q = C·U and the energy
W = 0.5·C·U^{2}.
Now, the capacitor is connected (parallel) to the same
uncharged capacitor (total capacity now C+C=2·C),
and the voltage will drop to U_{1} = Q /
(2·C) = U / 2.
Each of the capacitors has the energy W_{1} =
0.5·C·(U/2)^{2} = W / 4 and both
capacitors together have the energy W_{2} =
2·W_{1} = W / 2, which is
half of the energy W at
start, even if the wires are very thick and have very
little resistance.
Where is the missing energy
???
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