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"ELECTRICITY" AS QUANTITY IN PHYSICS
SOME PHYSICISTS' QUOTES REGARDING "ELECTRICITY" AND ENERGY
1999 W. Beaty

What is electricity? This question brings up a morass of conflicting information.

Well, how do scientists use the word? Let's cut through the morass and ask:

What is the scientific definition for the word "Electricity?"
We'd expect that physicists have a clear definition for "the quantity of electricity." However, it might suprise you to learn that the following sources are unanimous in saying that Electricity is not a form of energy. Instead, they agree that an electric current is a flow of "electricity." They also agree that electrons and protons carry charges of "electricity," and that quantities of electricity are to be measured in units of charge rather than units of energy. To measure the quantity of electricity, scientists use the SI unit called the Coulomb.

Also see: Table of differences: Electric Charge versus Electric Energy?

Quotations from:

  1. J. C. Maxwell
  2. J. J. Thompson
  3. R. A. Millikan
  4. M. Faraday
  5. G. J. Stoney
  6. A. Einstein
  7. CRC Handbook
  8. NIST, Int'l system of units (SI)
  9. Physics dictionaries and glossaries
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1. MAXWELL

In 1988 during my first research into the "true" definition of the word Electricity, I discovered an excellent quote from James Clerk Maxwell stating specifically that electricity is not a form of energy. The following is from Maxwell's A TREATISE ON ELECTRICITY AND MAGNETISM, 1891:


  Part I, ELECTROSTATICS, Chapter I DESCRIPTION OF PHENOMENA
  Conductors and Insulators

  "35]
  While admitting electricity, as we have now done, to the rank of a
  physical quantitity, we must not too hastily assume that it is, or is
  not, a substance, or that it is, or is not, a form of energy, or that it
  belongs to any known catagory of physical quantities.  All that we have
  hitherto proved is that it cannot be created or annihilated, so that if
  the total quantity of electricity within a closed surface is increased
  or diminished, the increase or diminution must have passed in or out
  through the closed surface."

<snip>

  "There is, however, another reason which warrants us in asserting that
  electricity, as a physical quantity synonymous with the total
  electrification of a body, is not, like heat, a form of energy.  An
  electrified system has a certain amount of energy, and this energy can
  be calculated by multiplying the quantity of electricity in each of its
  parts by another physical quantity, called the Potential of that part,
  and taking half the sum of the products.  The quantities 'Electricity'
  and 'Potential', when multiplied together, product the quantity
  'Energy.'  It is impossible, therefore, that electricity and energy
  should be quantities of the same category, for electricity is only one
  of the factors of energy, the other factor being 'Potential.'  "

(Also see Part 1, Chapter II, Definition of Electricity as a Mathematical Quantity, and Definition of the Unit of Electricity.

-----

Maxwell goes on to point out that *force* cannot be energy, because energy equals force times distance (if force was energy, then after we multiplied force by distance, the result could no longer be energy.) And in a similar way, *mass* cannot be energy because mass multiplied by height gives potential energy.

So even though Maxwell was writing in 1891, and even though electricity still contained many mysteries, science had progressed far enough to figure out that electricity and electrical energy were two different things.

Also take note that Maxwell defines "Electricity" as a measurable physical quantity, and not as a class of phenomena.

So what then is "electricity"? Of course Maxwell first defines all of his terminology elsewhere in his book. It's clear from the following text that Maxwell intends the word "electricity" to mean the same as our modern phrases "charge of electricity," or "electric charge" ...and that electric currents are therefore flows of "electricity:"

  CHAPTER II  Elementary Mathematical Theory of Statical Electricity
    Definition of Electricity as a Mathematical Quantity

 63.] "We have seen that the properties of charged bodies are such that the
  charge of one body may be equal to that of another, or to the sum of the
  charges of two bodies, and that when two bodies are equally and
  oppositely charged they have no electrical effect on external bodies
  when placed together within a closed insulated conducting vessel.  We
  may express all these results in a concise and consistent manner by
  describing an electrified body as "charged" with a certain "quantity of
  electricity" which we may denote by "e." 



2. THOMPSON

OK, what about J. J. Thompson, the discoverer of the electron? As we see below, he agrees with Maxwell and defines "electricity" not as energy, but as charge...
   "As the cathode rays carry a charge of negative electricity, are 
   deflected by an electrostatic force as if they were negatively 
   electrified, and are acted on by a magnetic force in just the way in 
   which this force would act on a negatively electrified body moving
   along the path of these rays, I can see no escape from the conclusion 
   that they are charges of negative electricity carried by particles of
   matter."    -  J. Thompson,   Phil. Mag, 44, 293 (1897)



3. MILLIKAN

How about Robert Millikan, the physicist who first determined the value of the electron's charge? He's yet another example of an expert who uses the word "electricity" to mean electric charge rather than electrical energy:
  "...Faraday found that the passage of a given quantity of electricity 
   through a solution containing a compound of hydrogen, for example, 
   would always cause the appearance at the negative terminal of the same 
   amount of hydrogen gas irrespective of the kind of hydrogen compound
   which had been dissolved, and irrespective also of the strength of the
   solution; that, further, the quantity of electricity required to cause 
   the appearance of one gram of hydroben would always deposit from a 
   solution containing silver, exactly 107.1 grams of silver.  This 
   meant, since the weight of the silver atom is exactly 107.1 times the 
   weight of the hydrogen atom, that the hydrogen atom and the silver atom 
   are associated in the solution with exactly the same quantity of 
   electricity."  R. A. Millikan, THE ELECTRON, 1917 p15
Throughout Millikan's book "THE ELECTRON," and also in his autobiography, Millikan consistently uses the word "Electricity" to mean electric charge, and saw electric currents as being flows of "Electricity."



4. FARADAY

And what of Michael Faraday himself? Does he believe in different kinds of electricity? Nope. In his book "Experimental Researches in Electricity" from 1839, Faraday investigates the nature of electricity and frequently uses the term "quantity of electricity" to refer to quantities of electric charge (rather than to quantities of energy.) As in Millikan's quote above, Faraday passes a certain "quantity of electricity" through an electrolysis apparatus to create a distinct amount of gas, or amount of electroplating. This is described in his publication "On the absolute Quantity of Electricity associated with the Particles or Atoms of matter." (Heh. He said Quantity of Electricity.) Today we call his discovery by the name "Faraday's Law."

In a section about " Identity of Electricities," p360, Faraday examines five electrical sources:

  1. Voltaic piles (batteies)
  2. Electrostatic generators and frictional charge sep.
  3. Coils and magnetic induction
  4. Thermoelectric generators
  5. Bioelectricity ("torpedo" ray, electric eel)
Then in the following passage Faraday concludes that all of these various "kinds of electricity" do not exist: instead there is just one type of electricity, but an electricity where the values of current and charge can differ...
  "The general conclusion which must, I think, be drawn from this
  collection of facts is, that electricity, whatever may be its 
  source, is identical in its nature.  The phenomena in the five kinds 
  or species quoted, differ, not in their character but only in degree;
  and in that respect vary in proportion to the variable circumstances of
  quantity and intensity ['intensity' means current -billb] which can 
  at pleasure be  made to change in almost any one of the kinds of 
  electricity, as much as it does between one kinds and another."  
  -Michael Faraday, EXPERIMENTAL RESEARCHES IN ELECTRICITY, vol.1, 1839, p360

See also: "Faraday as a Discoverer", John Tyndall 1869



5. G. Johnstone Stoney

Here's a quote from G. J. Stoney, who recognized the existence of the quantum of charge and named it the "Electron" in his paper "Of the 'Electron', or Atom of Electricity", Phil Magazine N5 V38 P418-420 Oct 1894


  In this paper an estimate was made of the actual amount of this most
  remarkable fundamental unit of electricity, for which I have since
  ventured to suggest the name electron.  According to this determination 
  the electron = a twentiethot (that is 10^-20) of the quantity of
  electricity which was at that time called the ampere, viz: the quantity 
  of electricity which passes each second in a current of one ampere,
  using this term here in its modern acceptation. This quantity of
  electricity is the same as three eleventhets (3 x 10^-11) of the C.G.S.
  electrostatic unit of quantity.



6. EINSTEIN

If you're swayed by authorities, then listen to Albert Einstein, from his 1938 book Evolution of Physics:
  "The electric fluid flowing through the wire is the negative one, 
   directed, therefore, from lower to higher potential... The next 
   important question is whether the structure of this negative fluid is
   "granular,"  whether or not it is composed of electric quanta.  Again a
   number of independent experiments show that there is no doubt as to
   the existence of an elementary quantum of negative electricity.  The
   negative electric fluid is constructed of grains, just as the beach is
   composed of grains of sand, or a house built of bricks.  This result 
   was forumlated most clearly by J. J. Thomson, about forty years ago.  
   The elementary quantity of negative electricity are called electrons."
   - Einstein/Infeld, EVOLUTION OF PHYSICS 1938, p 253
So even Einstein believes that "electricity" is not electromagnetic energy, but instead is the same as Charge (it is Coulombs rather than Joules.)



7. CRC Handbook of Chemistry and Physics

And how about the ultimate authority in physics? It's the CRC Handbook of Chemistry and Physics! (Heh. Well, most physicists rely on it as the ultimate authority.) What does the CRC Handbook say about the quantity called "electricity?" Is electricity the EM energy measured in Joules? Or is it the charge measured in Coulombs?

  Current CRC pages:
  http://www.hbcpnetbase.com/pdf/default.asp?id=02_07_91

  CRC Handbook, 64th Edition, 1984:

  Quantity of electricity or charge -- The electrostatic unit of 
  charge, the quantity which when concentrated at a point and placed at a 
  unit distance from an equal and similarly concentrated quantity, is 
  repelled with unit force...

  Coulomb (unit quantity of electricity) -- the quantity of 
  electricity transported in 1 sec by a current of 1 A.  A unit quantity 
  of electricity.  It is the quantity of electricity which must pass
  through a circuit to deposit 0.0011180g of silver from a solution of 
  silver nitrate.  An ampere is 1 coulomb/sec.  A coulomb is also the
  quantity of electricity on the positive plate of a condenser of 
  one-farad capacity when the electromotive force is 1 v.

  Electric charge (Q) -- The quantity of electricity; i.e., the 
  property that controls interactions between bodies through electrical 
  forces.


 

9. NIST Nat. Inst. of Standards, SI physics standards

The CRC defines "Quantity of Electricity..." as Coulombs. Also see the international metric system: the MKS Standards of the SI, and the National Institute of Standards and Technology (NIST) website, Table 3. They define "quantity of electricity" as charge measured in coulombs, not as energy measured in joules.
      Table 3.  SI derived units with special names and symbols

                                                            Expression in
                                                            terms of 
 Derived quantity                             Name   Symbol  SI base units

electric charge, quantity of electricity     coulomb   C       s * A




9. Various dictionaries of physics

Browsing through various physics glossaries and dictionaries, I find that most of them have no entry in section "E" for the word "Electricity." However, knowing that scientists throughout history used terms in very specific ways, I instead look under section "Q." Bingo! Most dictionaries have a listing for "Quantity of electricity..." also called electric charge and measured in Coulombs. A few even have it under section "C," where they define the word "Coulomb" as the unit quantity of electricity, or "A," where they define the Ampere as the unit for flow or transport of electricity. A quick google search finds them:
+"quantity of electricity" +definition



But what do today's scientists think of the word "Electricity?" Going further ahead in history we find that "Quantity of electricity" is still sometimes used in Europe, while American scientists mostly stop using the word. They replaced the term "Quantity of electricity" with "quantity of electric charge," then later shortened this to "quantity of charge." Scientists of today mostly use the term "electricity" as a chapter title, or use it in the same way as "biology" or "dynamics" to denote an entire class under which various phenomena are listed. Anything electrical then becomes a type of "electricity." So, over the decades "electricity" has <grin> stopped flowing in wires entirely! Instead electricity has turned into something like "physics" or "optics" or "weather." In the same way that wheels and bicycle chains are physics, batteries and wires "are" the electricity. Textbooks are full of electricity, but power lines and capacitors are not.

More instances of the scientific definition of Electricity:

 








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