# Re: power v energy measurements, was Re: SSTC does 10 foot sparks

```Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>

Hi John,

My first coil (a small one) pulled 65 watts at 140VAC and produced 11 inch
power arc at 120 BPS.  Using your process:

1.  65 watts for one second or 65 joules in one second.
2.  120 sparks for one second.
3.  65 joules/120 sparks = 0.54 joules per spark
4.  11 inch arc
5.  20.4 inches per joule.

Now using the JF equation:  1.7 * sqrt (65watts) = 13.7 inches.  I didn't
consider my coil all that efficient.

I think one problem with inches per joule is this implies that if you double
the joules, you double the inches which many of us know to not be true.
John Freau empirically derived equation suggest this is the case.

Example: Take a TC designed for 120 BPS at some power level.  Double the
power and double the Cp to keep BPS at 120.  Now the bang energy has just
doubled but the spark has only increased by a factor of sqrt2.  One could
conclude that a large powered coil would yield a lower inches per joule and
a small powered coil would favor a larger inches per joule.  The system is
just not linear.

Gerry R

> Original poster: "John Couture" <johncouture-at-bellsouth-dot-net>
>
> The calcs for my test were as follows.
> 1. My coil wattmeter showed 120 watts for one second or 120 joules in one
> second.
> 2. My coil output was 120 sparks for one second.
> 3. This gave 120 joules/120 sparks = one joule produced one spark
> 4. The spark was 8.25 inches long,
> 5. This gave 8.25 inches / one joule = 8.24 inches of spark for one joule
of
> energy input.
>
> If you substitute the variables of any size or type of coil correctly and
do
> the math correctly as above you will find that the 8.25 inches is a record
> that is hard to beat.
>
> All comments -  please show your calcs as outlined 1 to 5 above so I will
> understand what you mean..
>
>   John Couture
>

```