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Conservation of Energy; history



Here are some interesting, and not totally irrelevant, quotations from on
old high school textbook (copyright 1906, yes 1906). The authors are
Millican and Gale; everbody knows the experiment for which Noble prize was
aworded to the first author. Good reading for those who wonder about common
misconceptions (heat and work are forms of energy).

In my opinion this textbook (not its vocabulary) should be a model for all
those who teach physics to kids. A similar book with short explanations
of currently used devices would be more difficult to write but it would
help a teach scientific and practical at the same time.

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'In all mechanical devices of whatever sort the work expanded upon the
[simple] machine is equal to the work accomplished by it. This important
generalization is called "the principle of work" and was first enunced
by Sir Isaac Newton in 1687, in a scholium to the third law of motion. ...
In other words, if there were no friction, no work would ever be wasted.'
[I say that the work is treated as if it were a form of energy.] And they
say:] 'The energy of a body is defined as its capacity for dooing work.'

.... 'Before considering what becomes of this wasted work we shall consider
some of the factors on which friction depends, and some of the laws which
are found by experiment to hold in cases in which friction occurs. ... "

[After describing Joule experiments the authors write:] 'A Frenchman by the
name of Hirn was the first to make a carefull determination of the relation
between the heat developed by collision and the kinetic energy which
disappears. ... the amount of heat developed in the lead was measured by
observing the rise in temperature of ....'

[I wish Hirn was a phys-L-er; I would beg him to do the same for the
sliding blocks, unless Al convinces me that this is not necessary.

Then the law of conservation of energy is introduced] 'in the most general
way. The work done by the acting force is equal to the sum of the kinetic
and potential energies stored up plus the mechanical equivalent of heat
developed. In other words, whatever energy is expended on a machine of any
kind an exactly equal amount of energy always appears either as useful
work or as heat. ... The waisted work always appears in the form of
increased molecular motion ...'

[A little later heat is identified as 'molecular energy'. Two ways of
increasing the temperature of a body are identified as working and heating.
A new definition of calorie [without referring to water] is presented, it
is 'simply 42,000,000 ergs of heat energy.' A section on heat engines
begins like this.] 'Thus far we have considered only cases in which
mechanical energy [waisted work ?] is converted into heat energy.'

[Later they write:] 'The number of calories of heat which disappears in
the formation of one gram of vapor is called the heat of vaporization of
the liquid."
Ludwik Kowalski