RE: SCIENCE FAIR BOTTLE CAPACITOR ExPERIMENT HELP!!!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

The uF value of a bottle capacitor won't be affected by the type of liquid 
in it, unless the filling level differs.  The uF capacitance is a function 
of the glass thickness and area between the two "plates".

Different liquids will have different resistances, and this may be viewed 
as a resistance in series with the capacitor.  We want as low a value of 
resistance as possible.  High values of resistance make the capacitor 
"lossy".

As part of a bottle capacitor, unless you have some sophisticated test 
equipment (RCL bridge), it will be very difficult to measure the series 
resistance.  In theory, the losses due to the resistance will be reflected 
in the performance of the coil, so all other things being equal, measuring 
the streamer length will reflect the series resistance due to different 
liquids.  But streamer measurement is an imprecise and subjective exercise, 
and I doubt would result in any useful data.

Better to measure the resistance of equal volumes/shapes of 
liquids.  Beware that using an Ohm meter, you may get some electrolytic 
reactions which may color the results.

In practical terms, the choice of liquids won't make a measurable 
difference in a bottle capacitor, as long as it's a saturated solution of 
something like table salt, calcium chloride, copper sulphate, magnesium 
sulphate, etc, etc.

Gary Lau
MA, USA


Original poster: "Nightmare" <nightmare-at-bak.rr-dot-com>

I am going to see which liquid in a bottle cap is the best. like i will use
salt water in one test and gatorade(lots of electrolytes) for another. Can
someone tell me how I would compare which is better??? or how i would check
which is better?

I think i could compare uF ratings with different liquids in the bottle
caps,(i have no idea what uF is) how do i compare uF ratings, then i could
conclude which hs the best uF rating.