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# Re: CHAT: Need a word for these!

From: Christophe Grandsire Thursday, January 31, 2002, 7:59
```En réponse à Danny Wier <dawier@...>:

>
> E and V mean the same thing, potential difference (or voltage).
Not exactly, at least to me and other scientists in France. We use U (or
sometimes V) for a potential difference (a scalar, i.e. a value), V for the
potential itself (also a scalar), while E is used only for the electromotive
(or simply electric) field, which is a vector (an "arrow"), kind of a
generalisation of U for 3-dimension problems. It's E which is used in Maxwell's
Laws, the basic laws of electric and magnetic behaviour.

>
> But where exactly do the letters E and Z themselves come from?
>
E from "electric" in "Electric field". R is for resistance, while Z is for
impedance (which is a generalisation of resistance to be used with periodic
currents, and elements like condensators, which have an impedance but no
resistance). It's written Z because it's a complex number (a number using the
square root of -1 :)) ), and z is the normal label for complex numbers (like x
is for real numbers and n for integers). The main difference between resistance
and impedance is that impedance depends on the frequency of the current
(allowing to talk about low-pass, band-pass or high-pass systems) and doesn't
only damp or enhance a voltage but also dephases it. Of course, the impedance
of a circuit made only of resistors is equal to its resistance, but real
circuits always have condensators and/or inductors (even if those are only
parasitic), and that's what makes impedance interesting :))) .

He he, all that reminds me of my studies :)) . I've had quite a lot of classes
on electricity and electronics :)) .

>
> The sound [Lt] with L meaning a voiceless lateral fricative is a neat
> one, which
> makes me think of American Indian languages of the Western US and