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- Newsgroups: sci.physics
- Path: sparky!uunet!gatech!concert!samba!tenney
- From: tenney@med.unc.edu (Charles R. Tenney)
- Subject: Jacob's Ladders (was Re: What are those things called...)
- Message-ID: <1992Jul24.193306.23657@samba.oit.unc.edu>
- Sender: usenet@samba.oit.unc.edu
- Nntp-Posting-Host: addor.med.unc.edu
- Organization: UNC-CH School of Medicine
- References: <1992Jul23.214214.8574@microplex.com> <1992Jul24.134854.9052@lut.ac.uk>
- Date: Fri, 24 Jul 1992 19:33:06 GMT
- Lines: 37
-
- In article <1992Jul24.134854.9052@lut.ac.uk> A.J.Robinson@lut.ac.uk (Alan Robinson) writes:
- >In article <1992Jul23.214214.8574@microplex.com> hsk@microplex.com (Harjeet Kalsi) writes:
- >>
- >>I know I've seen them in physics labs (including mine when I was in school)
- >>but forgotten what this "box" with two antennas, that has a high
- >>voltage spark travelling between the antennas from bottom to top,
- >>is called.
- >>
- >
- >I think they're called Jacob's ladders, but I could be wrong.
-
- Yes, that's what they're called. I have one at home, made out of a neon
- sign transformer and some coathanger wire. Two wires are attached, one to
- each high-voltage terminal, such that they come almost together, then rise
- vertically, almost parallel but diverging slightly. On mine, the gap is
- about 1/4 inch at the bottom and 1-1/2 inch at the top (about 2 feet
- tall). The spark forms at the bottom, and the (ionized, therefore
- conductive) air in the spark is heated and so rises. The spark travels up
- to the top, and beyond, at which point it ceases to conduct and a new
- spark starts. It takes a bit of fiddling (run, unplug, bend wires, plug in
- again, etc.) to get it right so the gap is not too wide at the top, the
- spark doesn't rise to the top and stay there, etc. You need substantial
- couthangers (not the cheap thin ones) to make it work, the thin stuff has
- a tendancey to start vibrating.
-
- Lots of fun, and easy to build if you have a neon sign transformer. But
- if anyone decides to try this, FOR GOD'S SAKE, BE CAREFUL. 15 to 30 kV
- deserves a lot of respect, and due caution. Especially in an unshielded
- configuration. If you can't be careful, don't try it at all, and don't
- blame me for any accidents.
-
-
- --
- --
- Charles R. Tenney tenney@med.unc.edu | What would the UNC school of
- | Medicine want with my opinions?
- "My karma ran over my dogma." | What would I want with theirs?
-