Fluids in electric and magnetic fields: Pressure variation and stability

The variation of the hydrostatic pressure with position in a dielectric or magnetic fluid acted upon by electric or magnetic forces may be somewhat delicate. For instance, the dominant role played by the striction forces in fluids having positive susceptibility is a physical phenomenon whose importance does not seem to be sufficiently well-known. Closely related to the pressure balance is the thermodynamic stability problem. In this paper two examples are analysed in detail in order to elucidate the pressure variation and thermodynamic stability for dielectric, paramagnetic, and diamagnetic liquids.