# Re: Tesla Coil toroid Size

```John H. Couture wrote:

>   I was hoping that it would be possible to get some idea of the input
> energy in a certain spark length by this test. For example if the spark
> increased one foot and it was found that the input energy increased 2 watt
> seconds we could say the energy in the spark is apparently 2 watt seconds
> per foot of spark.
>   This could help verify some of the other methods we are using to find the
> watt seconds per foot of spark.  -JHC

The notion of 'watt seconds per foot of spark' is incomplete at best,
since the arc length is completely dependent upon the break rate, or
BPS.

Here's an example:  My primary capacitor is 0.225uF, and operates at
26kV.
The Vpri is *not* adjustable in this design, which means that the Ep is
independent of the break rate, and therefore is always 76 watt-seconds.

At a BPS of   1, the sparks at the toroid are about 2.5 ft long.
At a BPS of  80, the sparks at the toroid are about 4.0 ft long.
At a BPS of 350, the sparks at the toroid are about 25. ft long.

The coil gains a factor of 10 in spark length while the energy
per pulse in the primary remains constant, at 76 Joules!
The dramatic increase in spark length is due solely to the coil
exploiting the ion lifetimes at the higher break rates.  The
coil *DOES NOT* generate higher voltages at higher BPS values.
--

-GL
www.lod-dot-org

```