Re: 40MHz Spark Gap Behavior (fwd)

---------- Forwarded message ----------
Date: Tue, 21 Apr 1998 10:48:24 -0600
From: Bill Lemieux <gomez-at-netherworld-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: 40MHz Spark Gap Behavior


I hope I don't sound like I'm picking nits, but if you're going to
explain things, at least use your terminology correctly, or you'll
only confuse people further.  to wit:

> Isn't it true that power is determined by Watt-seconds, or Joules? If I
> look at  a discharge of anything, I'm going to see Watts-per-unit-time.
> Therefore, if one Watt, in one second equals 1 Joule, then 1 Watt in 1/2
> second =
> 1/0.5 = 2 Joules. 1 Watt in 1/4 second = 1/0.25 = 4 Joules, etc.

Good illustrative discourse, so far.  But then you go astray...
> Look at it like a rifle bullet. Assume that a given amount of gunpowder
> will produce a given amount of explosive force. 

Um, not quite.  FORCE=MASS*ACCELERATION, whether it be expanding gasses
or baseballs.  In this case, stored energy is released over either a
period of time (slow burning black powder for example) or a short period
of time (fast-burning nitrate powders).

> Cause the gunpowder to burn
> slowly, and all the force 

You mean energy, not force.  The force applied to the bullet derives
how quickly the energy is released, see your own (correct) explanation
joules above.

> will be expended over a great amount of time, and
> may never even build enough pressure to move the bullet to end of the rifle
> barrel. On the other hand, the same amount of force, 

Nope, the _force_ on the bullet is greater over a shorter period of
time, but
the total amount of energy stored in the gunpowder is the same.

Also note that your explanation falls down in that the powder burns
_because_ it is confined, and that any time you actually get the powder
the bullet _will_ move in a very spritely manner toward the muzzle
unless it
has been jammed in some spectacularly secure fashion, in which case the
gets to eat parts of the breech.  But never mind all that...

> expended in a
> microsecond, can propel the bullet so fast that simple air friction can
> turn the slug molten in flight. 

That's one hell of a firearm.  Melting projectiles with air friction is
in the regime of railguns.  The highest velocity cannon on the planet,
Israeli Mercava system with a muzzle velocity approaching 3000 MPS,
melt its projectiles in flight...

> Same amount of energy, same amount of
> force, much different levels of power :)

No.  The force is NOT the same.  If it were, the gun would violate F=MA.
If the force were the same, the acceleration would be the same.

> And how about your capacitors? If you bleed the energy off slowly through a
> resistance, you could literally power a DC motor for a while. Discharge the
> same energy all at once, and you can explode a motor in an instant ;) Same
> levels of energy, but greatly different amounts of power. :)

True, and agreed. Just wanted to clarify where you misspoke.


.                personal email: gomez-at-netherworld-dot-com                .
.          personal web page: http://www-dot-netherworld-dot-com/~gomez       .