2001-07-16 I for sure was confused by the first part. In esu, is capacitance measured in distance? His first example gives a "capacitance of 796 cm. I know this means centimetres, as the formula he gives divides area (100 mm) by the 4pi times the plate separation. In other words, square centimetres divided by centimetres. The next thing to catch my eye was the repeated use of the name Purcell. Doing an Altavista search on the word Purcell turned up a large variety of possible meanings (96 264), it is impossible for me to know what is meant here by the term. A link I came across leading to a University in Northern Arizona: http://purcell.phy.nau.edu/ Other links were to a composer Henry Purcell (1659-1695) Venturing a guess, I think it is a possibility that this Purcell mention in his reference must have been the author of a book from the days of esu's. This guy must be parroting this Purcell's material without consideration of the units being obsolete and totally replaced by SI. I guess, we'll have to wait to see if the author responds to Jim's letter. John Keiner ist hoffnungsloser versklavt als derjenige, der irrt�mlich glaubt frei zu sein. There are none more hopelessly enslaved then those who falsely believe they are free! Johann Wolfgang von Goethe (1749-1832) ----- Original Message ----- From: "James R. Frysinger" <[EMAIL PROTECTED]> To: "U.S. Metric Association" <[EMAIL PROTECTED]> Sent: Monday, 2001-07-16 18:56 Subject: [USMA:14435] Fwd: Physics 106, Spring, 2001 homework > I posted this message a few minutes ago. > > Jim > > ---------- Forwarded Message ---------- > Subject: Physics 106, Spring, 2001 homework > Date: Mon, 16 Jul 2001 18:55:53 -0400 > From: James R. Frysinger <[EMAIL PROTECTED]> > ... > > Dear Professors Groth and Nice, > > I was scanning some web pages on the internet this morning on the topic > of capacitors when I came across your homework solutions page at > http://phy106.princeton.edu/hwk_s01/hw03sol.pdf > Out of curiosity I have pointed some of my colleagues to this page, so > they might ask you about this separately. > > Immediately I was struck by the surprising realization that you are > using electrostatic units for at least some of your teaching and > homework assignments. This has stimulated my curiosity and some > questions come to mind. I haven't seen these units in print since I > read the journal articles written by Millikan a century ago regarding > his famous oil drop experiments. In fact, the use of esu's was > superceded so long ago that I cannot find the date on which they were > deprecated. Certainly, they were replaced when the SI was brought into > being forty years ago. I am on two IEEE standards committees (one > jointly with the ASTM) and I cannot recall ever seing those units used > in any of their materials. Nor can I recall their use in any AIP > publications in the last few decades. > > I would appreciate it if you would take a few minutes to satisfy my > aroused curiosity. Could you tell me why you still use them and also > what textbook support you have for your students on esu's? To that > point, what is the textbook assigned for this course? If you use esu's > I must assume that you might be using emu's as well. Would that be > correct? What do you tell your students about the use of esu's and > emu's in modern journal articles? > > Reading down several lines I see your comment that "the unit pF is > pronounced 'puff'". Is this an inside joke that you have with your > students or did you intend for that to be a valid comment? If the > latter is true, do you also encourage the use of "kilo" for kilogram > and "klick" for kilometer in your teaching of mechanics? Taking the > risk of offering unsolicited advice, I recommend that the use of > nicknames for SI units by the students (or anyone else) neither be > encouraged nor tolerated. > > regards, > James R. Frysinger > > -- > James R. Frysinger University/College of Charleston > 10 Captiva Row Dept. of Physics and Astronomy > Charleston, SC 29407 66 George Street > 843.225.0805 Charleston, SC 29424 > http://www.cofc.edu/~frysingj [EMAIL PROTECTED] > Cert. Adv. Metrication Specialist 843.953.7644 > > ------------------------------------------------------- > > -- > James R. Frysinger University/College of Charleston > 10 Captiva Row Dept. of Physics and Astronomy > Charleston, SC 29407 66 George Street > 843.225.0805 Charleston, SC 29424 > http://www.cofc.edu/~frysingj [EMAIL PROTECTED] > Cert. Adv. Metrication Specialist 843.953.7644 >
