Conservation and Innovation : Helmholtz's Struggle with Energy ...

principle taking this potential into account, in analogy with the case (previously
discussed) of the coupling of two magnets. But if we admit that potential we
would not be able to rededuce Neumann's induction law, a law that is empirically
corroborated. 221. In the second case terms unknown in 1847, but that indeed exist,
were not predicted.The usefulness of the specific application of the concepts of
tension and living forces is also questionable 222: what is the rational for defining
aAJdt as tension forces? The equation in fact for Helmholtz still holds if A = 0,
thus without tension forces. Moreover, what is the reason to call the product JdV
"the living force acquired by the magnet"? Helmholtz's efforts show thus that it is
impossible an a priori precise theoretical deduction of the energy equations:
experimental knowledge is required; on the other side, without a guiding
principle it is difficult to find and to interpret this experimental knowledge;
moreover the expression of the principle can offer a ground for comparison for
theories experimentally equivalent.
This basic principle-theory-experiment interplay present in the Erhaltung will be
permanently connected with the subsequent developments of the energy
conservation theory. It is always difficult to take into account the different forms
of energy involved in a specific process, and impossible to find the ultimate
result 223.
At the end of the section Helmholtz asserted that for some more complicated
cases discussed by Neumann and Weber the principle cannot give precise
determinations, but only qualitative indications, also because of the lack of
experimental results 224.
8 Conclusion
Pp.111 and 114.
221 See Planck Princip Pp.45-6.
222 It was in fact discussed in Helm Energetik Pp.45-7.
223 On the impossibility of a "primary" expression of energy see: Planck Princip
224 The electromagnetic equations will be revised and rediscussed in 1854 during the
controversy with Clausius.