Dissociative Identity Disorder

Denis McMahon:

I can't explain acceptable voltage drop other than to explain that "voltage drop" is not an acceptable expression for an analytical engineer. My physics teacher, long ago  in school days, would mark our homework down if we used that expression. The correct expression is "potential difference". He would rig up glass accumulator cells, connected in various bizarre ways, and then check across various pairs of terminals with a voltmeter, to ram home the point. (Which he did very effectively - I remember those classes as though they were yesterday.)


Even the term "voltage" was not acceptable. We don' say "ohmage" for resistance, or "amperage" for current. (Well maybe we do for some specific commercial purposes, but not for formal engineering.)  "Voltage drop" is about as logical as "position displacement" for distance.

 

You can whinge about terminology all you like, but my Collins English Dictionary lists both "voltage" and "amperage" as words.


Trying to explain "voltage drop" is a lot easier than something like "difference in potential difference".

Rob Eagle:


(ii) Uh?

(iii) Uh?





 

When someone puts up a post discussing the importance of us all having respect for the sanctity of human life, it would be extremely difficult to imagine a more graphic example of a 'lack of' respect for the sanctity of human life than the two responses above!

Rob Eagle:

"Lack of respect for the sanctity of human life", well that's a though one!  I think that one's a bit above my pay grade as they say, I didn't design life so I have had little input into it and also to whether it should be respected at a sanctity level.  There is one thing that is an absolute certainty in life though and that is one day you will die, so, so much for respect for life there then.

So you don't agree that 'having respect for the sanctity of human life' was the reason for writing a set of regulations in the first place then?

Rob Eagle:

. . .

Volt drop - volt drop limits, for installations, are defined in 7671, other than that it depends upon the equipment itself and its tolerance to voltage fluctuations, switch-mode power supplies, for example, generally work anywhere in between 90 - 260V so fairly tolerant to volt drop at 230V, other things may not be so, i.e. lamps. 

Now we are getting somewhere! Fluctuation in supply pressure, as compared with drop of potential along a conductor. Not the same thing. We need to be sure what we are talking about. I agree that in this case we need a simple term to describe what is happening. "Electro-motive force deviation" is too ponderous a term. If we need to quantify this, there is surely no harm in stating the quantifying unit?


I do maintain that my physics teacher was right in discouraging the term "volt drop" in analysis of an electrical network, even though the penalty may have been a bit heavy. I discouraged it myself in my lecturing days. Students using the expression in an ambiguous way tended to lose the plot.


One problem is that some basic units of measurement have no formal definition; we must use some inadequate synonym, e.g. "electrical pressure" for electro-motive force. Hence the customary usage of simple terms like "voltage". It does no harm where we need no rigourous analysis. "Potential" is of course a word with a broader meaning - "capability of achievement".  


It is interesting to note that in devices like motors, transformers, etc., engineers sometimes use the term "back e.m.f." rather than "back voltage". Perhaps because this is rigourous analysis.

Simon Barker:


. . .

You can whinge about terminology all you like, but my Collins English Dictionary lists both "voltage" and "amperage" as words.


Trying to explain "voltage drop" is a lot easier than something like "difference in potential difference".

Dictionaries are very useful but they are not everything. I checked in the Concise Oxford Dictionary; it also contains the words "amperage" and "voltage". Is a dictionary a book of rules of language, or is it a representation of customary practice? I think the answer is somewhere between these extremes.


Let us look at another example - "footage". This is sometimes used to refer to period of run of cine film. I once read somewhere that celluloid film passes through the projector at a speed of approximately one foot per second, so the time and length become interchangeable. The term has stuck with electronically generated moving pictures. I suppose "secondage" does not roll of the tongue so easily, though it would be more to the point.


Here are some other examples of "age" appended to a unit name, which are or are not in popular usage.

In use                                   Not in use

mileage    distance            knottage  nautical speed

acreage  land area            chainage  distance

wattage  power                  joulage  energy

poundage  surcharge        dollarage  !

tonnage  cargo capacity    grammage  mass


We may need to form our own conclusions why some of these expressions have caught on and others have not.