What the HECK is that? Number 3.

Please note the official change of the title of this game, it is no longer "what is this".

Here is the item:


I suspect someone will know what this is. Honestly, I didn't figure it out right away. However, I have found that the readers as a group generally are more knowledgeable than me by myself.

Oh, I don't think there is really much description to add here. I included a meter stick for scale.

P.S. How come a device for measuring temperature is a thermometer and a device for measuring electric potential is a voltmeter? Shouldn't the meterstick be called either a length-meter or a meter-meter? If you use the Queen's English, I guess that would be metre-metre.

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I've used this. It is a power supply for a plasma tube. You stick the terminals in the top and bottom clamps, turn out the lights and grab your diffraction grating. Ours tend to shock people, so we got new ones, but for some reason we haven't thrown away the old ones.

Actually, in the Queen's English it would be a metre-meter!

How come a device for measuring temperature is a thermometer and a device for measuring electric potential is a voltmeter? Shouldn't the meterstick be called either a length-meter or a meter-meter?

The word "meter" is derived from the Latin and/or Greek word for "measure", so it would have been used for any device specifically introduced for the purpose of measuring something in a lab. Yardsticks (the predecessors to meter sticks) were primarily used outside of laboratories (for instance, to determine how much cloth you were buying), and more generally by the merchant class rather than the aristocracy (who were the only people who could afford to do science at the time), so we are stuck with the Anglo-Saxon terminology.

The term "ruler" is related to a specific use of "rule" to mean a straight line drawn on something, a usage which you are most likely to encounter when buying paper that you intend to write on (you may have also encountered it if you use LaTeX). You use a ruler to draw a rule (by hand) on a piece of paper.

By Eric Lund (not verified) on 03 Sep 2010 #permalink

Fran beat me to it, but yeah, I knew what it was right away. That particular model seems to be more flexible in what tubes it will accept in exchange for being potentially dangerous; I wonder how close you could get those two clamps before they'd strike an arc in room air?

Rats! Too slow. I recognize this as well. I *heart* old physics equipment! Amazing (or scary?) that the new ones come with explicit directions to *not* put your fingers in the sockets :)


the breakdown voltage of air is about 100kV per meter.

if the power supply can put out, say, 10kV, you should be able to put them about 10 cm apart and get a spark to jump the gap.

it is more likely the power supply only puts out a couple hundred volts to several kilovolts, so you are probably realistically looking at a few centimeters or less to get a spark.

Rhett, we want to see video of an experiment using air and, say, vaporized copper! Put a heavy copper rod on each end and decrease the distance until it gets interesting. Just remember to unplug it before moving the electrodes ....

Other random thoughts.

Will these appear every Friday morning?

Breakdown in dry air is 3 MV/m DC, but more like 200 kV/m in August. Does the value for AC depend on frequency? Where can I look that up?

I'm going to have to start using metre-meter in class.

You should have asked how to measure electrical potential with a potentiometer ... without the help of another "meter".

I'd wager that we use "voltmeter" because people were measuring volts before they decided what it was. Besides, I would expect a potential-meter to have a "stat volt" setting. But then I'm the kind of person who complains that it they don't make protractors in radians.

I've actually looked, and my memory says that our spectra tube power supplies kick out 5 kV. Is yours? Ours also have an "on" lamp. I wish I had one of yours so I could point out the value of modern Nanny State safety warnings. They sure beat plugging the thing in and then asking "I wonder what this does?" I use that sort of comparison with two versions of a device (one safe, one not) that I won't mention here because it is a good candidate for this blog subject.

I should've read better, it says 'power supply for a plasma tube'

By Cleon Teunissen (not verified) on 04 Sep 2010 #permalink

I am just trying out your new predictions platform.
This is interesting for Collective intelligence purposes and well done.
Could I have more background information on that project? Having worked at Yahoo!
Answers, Flickr and Community products out of Canada, I like to discover interesting projects like this.

@Fran, Hah! I didn't even intend that as a joke. Maybe my facility with unintentional puns is why everyone is always laughing at me...