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[Phys-L] Re: A battery cell



Don't forget, or how about mmf (magnetomotive force.)!

bc

Clements, Gregory wrote:

In trying to find the origin of the term electromotive force I came a=
cross this material in a history of science book in my collection. "=
Science, The Never-Ending Quest", by William Vergara, 1965, pages 296=
,297 "Ohm noticed almost immediately that if a number of voltaic cell=
s are connected in series ... the current increases as additional cel=
ls are added. The current is then proportional to the number of cell=
s in the battery. Here was a clear connection, at last, between the =
tension of a battery and the current it can produce. ... His analogy =
was the flow of heat along a metal wire or rod. ...The similarity bet=
ween the flow of heat and the flow of electric current suggested the =
introduction of a quantity whose behavior in electrical circuits was =
similar to that of temperature in the theory of heat. That quantity =
was the tension of a voltaic cell .... Ohm called it the electroscopi=
c force of a cell, and it is now called an electromotive force. ... O=
hm published his conclusions in a book and in a series of scientific =
papers between 1825 and 1827."

=20

I did a quick search through my collection of old physics books. The=
relevant results are listed below. The title, author, printing date=
and page references are listed for each book. The potential differe=
nce is referred to as "intensity or tension" in sources 1,2,3,4. The=
earliest reference I found to the term "electromotive force" is in a=
book printed in 1881. Sources 5 - 8 give examples of the use of the=
term. Source 9 speculates on the origin of the term.

=20

The Natural Philosophy books I have that were printed before 1840 gen=
erally have less specific statements about potential difference and m=
uch less discussion on electricity that the books printed after 1840.

=20

I also did some searching at goggle that led to these web sites:

=20

http://www.electricityforum.com/electricity-history.html

This web site credits Kirchoff with deducing that Ohm's electroscopic=
force and electrostatic potential are identical.

=20

http://www.sizes.com/units/volt.htm

"The cgs <http://www.sizes.com/units/sys_cgs.htm> unit of electromot=
ive force (e.m.f.) was based on an idea of F. E. Neumann in 1825. On=
e cgs unit of e.m.f. was produced in any electric circuit cutting one=
magnetic line of force per second. " (See the following site for=
clarification on the date...Greg Clements)

=20

http://www.sp.phy.cam.ac.uk/teaching/em/inductn.pdf

This site gives 1845 as the date for Neumann's conclusion. Since Far=
aday discovered electromagnetic induction in 1831 I think the 1845 da=
te is probably correct.

=20

Greg Clements

Midland Lutheran College

clements@mlc.edu

=20

=20

1. "A Compendium of Natural Philosophy" by Denison Olmsted, 1848, pag=
e 217 "The term electricity is used to denote both the unknown cause =
of electrical phenomena, and the science which treats of electrical p=
henomena and their causes."

page 241 "The object of the battery is to accumulate a great quantity=
of the electric fluid, which is in proportion to the extent of surfa=
ce; the intensity, or elastic force, as indicated by the quadrant ele=
ctrometer, is no greater in the battery when charged, than in a singl=
e charged jar."

The book does not use the term electromotive force.

=20

2. "The Science of Common Things; A Familiar Explanation of the First=
Principles of Physical Science" by David Wells, 1857, page 292 "The =
electricity developed by the action of a single pair of plates immers=
ed in acid water is very feeble: how can it be increased? By increas=
ing the number of the plates and the quantity of the liquid, we incre=
ase the intensity of the electricity developed." This book does not =
use the term electromotive force.

=20

3. "An Introduction to Natural Philosophy" by Denison Olmsted, Revise=
d by E.S. Snell 1869, page 369 "The great difference between the galv=
anic and the frictional electricity is, that the latter is in a state=
of great intensity, or tension, as it is often called, darting viole=
ntly, and with the evolution of sound and light, through an obstructi=
ng substance, while the former has very low tension, flowing in a com=
paratively gentle stream through conductors, and unable to pass acros=
s interruptions, unless they are exceedingly small." This book does =
not use the term electromotive force.

=20

4. "Fourteen Weeks in Physics" by J. Dorman Steele, 1879, page 233 "E=
lectrical Potential is a property of a body by which electricity tend=
s to go from it to another, and is measured by the resistance met in =
the passage. This term is to electricity what temperature is to heat=
."

page 235 "A battery may develop a great quantity of electricity havin=
g a low degree of intensity, or a small quantity having a high intens=
ity. .. The intensity of the electric force depends on the number of =
cells; the quantity, on their size." This book does not use the ter=
m electromotive force.

=20

5. "Elements of Natural Philosophy, A Text-Book for High Schools and =
Academies" by Elroy Avery, 1881, page 239 "Experiments show that the =
quantity of electricity passing in a unit of time, over a given condu=
ctor, is directly proportional to the electromotive force. (This elec=
tromotive force, 'E.M.F.,' is the supposed force that causes or tends=
to cause a transfer of electricity from one point to another.)"

=20

6. "School Physics" by Elroy Avery, 1895, page 424 "Whenever a positi=
ve charge is placed upon a conductor, it raises the potential at the =
point of application, and there is a flow of electrification until th=
e surface of the conductor is an equipotential surface. If two condu=
ctors at different potentials are connected by a wire, a transfer of =
electrification will take place until the difference of potential dis=
appears. Whatever its nature, the agency that tends to produce such =
a transfer is called electromotive force.

page 443 "As hydraulic pressure might be called water-moving force, s=
o electrical pressure is called electromotive force (E.M.F.) The unit=
of electrical pressure is called the volt, and is almost the same as=
the electromotive force of a cell consisting of a copper and a zinc =
plate immersed in a solution of zinc sulphate."

(By the way, this book does not mention the electron.)

=20

7. "Elements of Physics" by George Hoadley, 1908, page 312 "The diffe=
rence of potential at the terminals of a cell when it is on open circ=
uit is its electro-motive force, or E.M.F."

=20

8. "A First Course in Physics" by Robert Millikan and Henry Gale, 191=
3, page 247 "The potential difference which a galvanic cell or any o=
ther generator of electricity is able to maintain between its termina=
ls when these terminals are not connected by a wire, that is, the tot=
al electrical pressure which the generator is capable of exerting, is=
commonly called its electromotive force, usually abbreviated to E.M.=
F. The E.M.F. of an electrical generator may then be defined as its =
capacity for producing electrical pressure, or P.D.

=20

9. "Physics A Textbook For Colleges" by Oscar Stewart, 1931, page 453=
"Electromotive force has a misleading name, for it is not a force bu=
t a work factor; when multiplied by quantity, it gives work. ... The=
name had its origin in the analogy of an electric current to the flo=
w of a liquid."=20

=09----- Original Message -----=20
=09From: Ludwik Kowalski <mailto:kowalskil@MAIL.MONTCLAIR.EDU> =20
=09To: PHYS-L@LISTS.NAU.EDU=20
=09Sent: Monday, February 28, 2005 9:57 AM
=09Subject: Re: A battery cell
=09
=09

=09
=091) It would be useful if somebody with an easy access to very old
=09physics texts could trace the history of the term "electromotive
=09force," and share the result with the rest us. For the time being =
let
=09me speculate.
=09



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