An experimental analysis of electromagnetic forces in liquids

Three theories are outlined to explain the observed forces in fluids. A system-atical analysis, via a number of appropriate experiments with liquids, shows that only one of them is substantially correct. A new method for studying the electrostriction in liquids is presented. Although the technological importance of the electromagnetic forces in fluids seems to be rather secondary, it has been an exciting subject of controversy during the last hundred years. We must say that there is no reason to consider this as an open problem any more: a long series of experiments scattered along the years show conclusively that the actual electromagnetic force density on a neutral fluid, without any macroscopic current in it, is given, within a reasonable degree of approximation, by the concordant theories with Note that SI units have been used with the definitions p=popr T = mass density. Let us recall that, in all the experiments up to date, the difference e =A-f1 is experimentally undetectable in the gas case (Jaumann and Stipa 1934) as well as in all para-magnetic liquids. In the case of high permittivity liquids e is negative when ae,/i% is measured along an adiabatic curve and positive when the isothermal quantity (aEr/&)T is used. Its actual value, in any case, is relatively small (Bruhat 1962), and only after 1994