• Home
• Biography
• Other Interests
• Quotes
• Publications
• Comments

George Caplan's Research Projects

Three-Phase and Six-Phase AC at the Lab Bench

Utility companies generate three-phase electric power, which consists of three sinusoidal voltages with phase angles of 0, 120, and 240 degrees. The AC generators described in most introductory textbooks are single phase generators, so physics students are not likely to learn much about three-phase power. I have developed a simple way to display the waveforms of the three-phase power supplied to my lab and to demonstrate some interesting features of three-phase power. The waveform displays require three small transformers, a Vernier LabPro (R) data collection device, and a computer; but the demonstrations require only the transformers and some miniature light bulbs. I have also developed a way to demonstrate how six-phase AC can be derived from three-phase AC.

The following article has been submitted to the The Physics Teacher. After it is published, it will be found at http://scitation.aip.org/tpt.

>>Learn more
>>Download article

Which String Breaks?

In The Physics Teacher for October 1995 (p. 478) Martin Gardner called attention to the well-known demonstration in which a large mass is suspended by a light string, with a similar string hanging from the mass. If you pull slowly on the lower string, the upper string breaks. But if you pull rapidly, the lower string breaks. Most introductory physics textbooks give some version of this problem in qualitative form, but we are not aware of a quantitative treatment that shows what parameters determine which string breaks.

Copyright 1996 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in M.A. Heald and G.M. Caplan, Phys. Teach. 34, 504 (1996) and may be found at http://link.aip.org/link/?pte/34/504.

>> Learn more
>> Download article

Ye Olde Inertia Demonstration

A simple quantitative analysis of the classic inertia ball demonstration explains why the lower string may break for "jerks" weaker than those that normally break the upper string, and why both strings may break-first the lower, then the upper.

Copyright 2004 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in G.M. Caplan and M.A. Heald, Am. J. Phys. 72, 860 (2004) and may be found at http://link.aip.org/link/?ajp/72/860.

>> Learn more
>> Download article

Simple DC Power Supply

If you want to make a neon-bulb relaxation oscillator, but don't have a dc power supply that will produce the required 80 V or so, here is another option. I created a 95-V battery to use with a relaxation oscillator by connecting ten 9-V alkaline batteries in series. The batteries snap together like Lego bricks, and the leads on the end batteries each use half of a two-terminal battery connector. This dc power supply is safer and more convenient than one running on 110 VAC.

Copyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in George M. Caplan, Phys. Teach. 46, 57 (2008) and may be found at http://link.aip.org/link/?pte/46/57.

>>Download article