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Re: 50%



	I agree with Bert's model.  There is no problem at all
in getting very close to 100% energy transfer in a reactively
coupled circuit with low losses; that's how almost all RF coupling
circuits work.  The "two capacitors shorted together" model gets
into trouble because, if there is zero resistance, an infinite
current flows through zero resistance for zero time!  Add an
arbitrarily small amount of resistance in the circuit and  conventional
circuit theory works fine and all of the "missing energy" turns
up as heating of the resistance.
	Consider a very simple model, such as is found in "boost"
type switching voltage converters.  Connect a low-loss inductor
in series with a battery. The "free" side of the inductor is
connected to a capacitor through a diode such that the inductor
is connected to the positive terminal of the battery, the capacitor
ground end to the negative, the anode of the diode to the "free"
end of the inductor, and the cathode to the floating end of the
capacitor.  Switch the free end of the inductor to ground and let
current build up (i=E/L*t).  After some period of time open the
switch which ground the inductor.  The voltage across the inductor
will rise (instantaneously) to a voltage which causes the same
current to flow into the capacitor through the diode.  As time 
goes on the current will flow until the capacitor until all of the
energy stored in the inductor (1/2 * LI^2) is now stored in the
capacitor (1/2 * CV^2), the current AND THE RATE OF CHANGE OF
CURRENT have dropped to zero.  All of the energy stored in the
inductor has now been transferred to the capacitor, and the circuit
is in steady state.  To the extend that there was finite resistance
in the circuit there will have been a small energy loss, but that
can, in principle, be made arbitrarily small without invoking any
extraordinary laws of physics.  This example is analogous to the
tesla coil when the current in the primary is interrupted at the
correct time.  In my 1915 "Wireless" text by Zelenick there are
photos of primary and secondary voltage waveforms, taken with the
very crude apparatus of the day (in some cases just neon bulbs
observed with a rotating mirror to provide a time sweep) which
clearly show the phasing of the "beats" in the primary and
secondary circuits.
For what it's worth,
Ed Phillips