[TCML] Spark gaps (again)
dexterlabs at dcemail.com
Mon Mar 9 02:35:51 MST 2009
Sorry ,neither do I have the books you are referring to.
Conductivity of the ionized plasma increases very fast yes .
But the resistance of the arc in gap depends of the effective
column cross-section,which doesn't change so fast as you desribe.
Expanding shock wave expands radially with velocities in the order of 1 Mach.
How much time it takes to expand from diameter 0.1 mm to diameter
10 mm calculate yourself.
--- jimlux at earthlink.net wrote:
From: jimlux <jimlux at earthlink.net>
To: Tesla Coil Mailing List <tesla at pupman.com>
Subject: Re: [TCML] Spark gaps (again)
Date: Sat, 07 Mar 2009 15:56:16 -0800
Dex Dexter wrote:
> Yeah,but the dynamic "resistance" of the gap isn't only the function of current.
> Beside other things,it's the function of time.That was my point.
The arc column heats up very fast (sub-microseconds). I don't have it in
front of me, but Edgerton's book or Bazelyan and Raizer probably have
the data. The conductivity increases so fast that when you're looking
at charge moving to the end of a leader; the propagation velocity of the
electromagnetic field in a leader is significant, more than the time it
takes to heat the air up.
Looking at the usual tesla coil running at 100kHz or so, a time scale of
a microsecond is instantaneous.
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