Dear Bill, What a delight it is to correspond to this list. I get the opportunity to learn about applications of SI outside my limited areas of knowledge, and you get the opportunity to explore the detail of practice in areas of your obvious professional expertise, and we both win. As I said it is a delight to have had this interchange. Thank You, Pat Naughtin CAMS Geelong, Australia on 2001/08/13 13.16, Barbara and/or Bill Hooper at [EMAIL PROTECTED] wrote: > Continuing to comment on your repsonse to my earalier message (my first > comments got too long so I split them): > > You wrote: >> >> In my experience, we are always better off sticking with the more >> technically correct quantity names and unit names even though their use may >> be a little more difficult. > > I agree completely! > > You went on: >> Returning to the issue of 'voltage'. >> >> What voltage will the battery need to be? >> ... >> >> What concepts have we lost here because of our choice of the word 'voltage'? > > I'll deal with just one of the examples you listed. > > By not using separate terms like "potential difference" (PD) and > "electromotive force" (emf) we have lost the ability to ask the right > question. The question "What voltage will the battery need to be" is > inadequate because a battery cannot be said to have a voltage that it > supplies. It has an emf. That emf may or may not be able to produce the PD > needed to operate the item you plan to operate with it. You can't light a 9V > light bulb with a 9 V transistor battery because a 9 V transistor battery > will produce about ZERO volts of PD. The transistor battery has an emf of 9 > V but it will not produce a PD of 9 V when it is connected across the 9V > light bulb. Basically, just knowing the voltage of a battery does not tell > you what it can deliver. You need to buy a different kind of 9 V battery if > you want it to deliver 9 V of potential difference when you connect it to > something that draws a lot of current like a light bulb. (Transistor > batteries deliver 9 V in appropriate electronic circuits precisely because > electronic circuits require such exceedingly small currents.) > >> >> I think that the quantity names 'potential difference' and 'electromotive >> force' contain useful distinctions and I would encourage their use in all >> appropriate circumstances. I am not able to suggest a suitable quantity name >> that would effectively combine these two concepts. > > I agree. I would prefer NOT to have a single term for both. I was not > proposing that. I was only stating that it is the de facto situation. > > I believe we agree > > ( 1) that "-age" words are undesirable, > > (2) that different words should always be used for different things (mass > and weight comes to mind again!), > > (3) potential difference amd electromotive force are awkward terms, an > > (4) we wish they could be replaced (by TWO new terms), > > We seem to disagree only in my acceptance of > > (1) the de facto but admittedly undesireable practice of using "voltage" for > PD, and > > (2) the de facto and even MORE undesirable practice of using using "voltage" > for emf at the same time. > > It's been a stimulating discussion, Pat. > > Cheers! > > Regards, > Bill Hooper > > ============ > Keep It Simple! > Make It Metric! > ============ > >
