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Real data from real experiments.



All,

I took the time out to repeat two experiments which few seemed to do but 
a lot have commented on.  I performed the first experiment presented here 
over a year ago and the latter experiment 5 years ago.  So I repeated 
with fresh data and first rate instrumentation.

Experiment #1  2 Capacitor charging problem.

Instrumentation;  Keithley 242 precision laboratory regulated supply.
		  Keithley 615 precision digital electrometer 
		  (1 teraohm input resistance)
		  B&K Precision 875A digital LCR meter
		  Beckman 310 digital voltmeter

All test common data:

  Two caps are arranged with the minus terminals strapped permenantly 
together with both the minus of the electrometer and the minus of the 
supply connected to same.

postive lug of the charged cap was connected to the supply with a 
temporary hook connector with series 10K ohm resistor to limit inrush 
current. This hook could be removed after charge level was determined.  
Also permenantly connected to the positive lug of the charged cap was the 
positive lead of the electrometer.  This was used to determine charge 
voltage of the capacitor prior to transfer of charge to the discharge 
capacitor.  finally, also connected to the positive lug was a single pole 
knife switch with was normally left open during charging.  the other end 
of this knife went to the uncharged capacitor. The uncharged capacitor ws 
temporarily shorted with a heavy lead to assure no residual charge and 
then removed just proir to the test.


Test A

Capacitors used: 

 Specially selected (from 30 identical capacitors) modern Mallory
1800 ufd 500 volt electrolytics. 3" diameter by 9" tall Selected using 
LCR meter so the two caps used differed in value by 0.4%.  (1814 and 
1821ufd)  Both capacitors assumed to be relativley lossey and loaded with 
internal inductance.

The set up was charged a measured 99.95 volts as read by the digital 
electrometer.  The Beckman voltmeter was used to cross confirm this. the 
hook charging lead was disconnected from the supply.  The knife was 
closed.  A loud explosion occured with bits of molten copper bouncing 
around on the bench top. immediately the electrometer was read and the 
final voltage was 49.76 volts the beckman was then connected and the 
reading verified to within .5%.  The electrometer was left connected to 
the now joined pair of capacitors and after 20 minutes read 49.58 volts.

A second test was made where the only change was a 20K ohm resistor was 
placed in series with the knife to allow for slow charging of the 
uncharged capacitor.  the knife was opened and the hook reconnected to 
the supply.  a shunt was used to short out the capacitor to be charged 
and was left in place for 2 minutes to assure 0 charge retention.

Again the hook was disconnected from the supply when the charged 
capacitor read 99.93 volts.  The knife was closed and absolutely no 
visible spark or noise was noticed.  The electrometer fell over the 12 RC 
time constants allowed prior to taking a "finished reading".  The volatge 
at the end of this period read 49.82 volts. Again confirmed to within 
.5% by the Beckman voltmeter.  After 100 time periods (50 minutes) the 
voltage read 49.12volts.

Test #2

Two superb high energy .03ufd discharge storage capacitors which were 
custom wound for me by NWL with a measured internal inductance of 25 
nanaohenries were now used.  They measured .0316 and .0317ufd 
respectively.  Same setup as above.  first test was a solid wire knife 
switch circuit.

The charged capacitor was charged to close to 1000 volts.

The main capacitor read 1087.0 volts prior to supply charging hook 
removal and knife closure.  A rather smallish but noticable pop and 
sparking were noted at closure.  The electrometer read 543.2 volts.

The 20K ohm resistor ws plased back in the knife circuit.  the same 
routine of disharge of the cap to be charged was observed and the main 
cap charged to 1086.2 volts and the knife closed with no noise or spark. 
After many thousands RC time periods. (2 seconds)  the electrometer was 
read on the electrometer to be 542.8 volts.  The Beckman could not be 
used here because of its heavy 10 megohm loading of the circuit.  Only 
the electrometer could play this game.  after approximately. 1 million 
time constants  (10minutes) the electrometer read 520.4 volts.

Conclusion:

The voltage on any capacitor discharging into an identical capacitor with 
divide by 1/2 or equal 50% of its original voltage regardless of massive 
blasting of copper to molten beads in the exchange or a kinder, gentler 
flow of charge through limiting resistances.  1/2 of the original stored 
energy (1/2cv^2) is aboslutely and irrevocably lost in this situation to 
a plethora of forms of waste energy given off to the evironment and 
circuit components.  Charge is conversed as well as energy.  The energy 
transfer to the other capacitor will forever undergo a 50% loss factor.



Experiment #2

A barium titanate capacitor was removed from its epoxy housing.  the 
block of titanate was .810" thick and 1.77" in diameter. Two 2" brass 
disks were used as plates to contact both sides of the slug. The B&K LCR 
meter ws used to measure 4.72nf of capacitance (originally it was a 480nf 
capacitor dielectric constant k~1200.)  A 4 pound lead weight was 
consistently used as a compression force device.  Two sheets of 5 mil 
thick virgin mylar (k=3.5) 2" in diameter were sandwiched between the two 
brass disks and a reading of 1.51nf was recorded.

Next the stack consisted of disk-mylar-titanate-mylar-disk (as in a water 
capacitor being shielded from the plates by thin membranes of plastic.)
Now the reading for the total group was .99nf.

Conclusion:

Regardless of the dielectric constant of a superior dielectric, any 
insertion of a dielectric of vastly lower value, even if very 
thin compared to the superior dielectric, (in this case 81 times 
thinner), will drag the final value of the resultant capacitor down to a 
level even below that of a capacitor made up of only the weaker 
dielectric material!  There are no free rides.  The game is rigged!


DO THE EXPERIMENT!  (Benjamin Franklin)


Richard Hull, TCBOR