A "perpetual motion machine of the second kind", although one of obviously no practical use, can be based on the following effect. If a constant-charge parallel-plate capacitor is immersed in a liquid dielectric, e.g. water:

http://www.spiraxsarco.com/images/re...Fig_3_16_9.gif

the force of attraction between the plates SHARPLY DECREASES - for water, it becomes 80 times weaker. However, if instead of liquid dielectric one thrusts some solid dielectric between the plates, the force of attraction the plates exert on one another (slightly) INCREASES. In both cases the dielectric between the plates - liquid or solid - polarizes and the picture of polarization is quite standard; yet when the dielectric is liquid (water) the force of attraction between the plates decreases by a factor of 80 while in the case of solid dielectric the force of attraction increases. Where does the drastic difference come from?

Two things are su 1. The sharp decrease of the force of attraction in the case of liquid dielectric "cannot be explained by electrical forces alone". 2. In the case of liquid dielectric, a "mysterious" pressure emerges between the plates that pushes them apart and so counteracts the original electric force of attraction between them:

http://www.amazon.com/Classical-Elec.../dp/0486439240
Classical Electricity and Magnetism: Second Edition (Dover Books on Physics), Wolfgang K. H. Panofsky, Melba Phillips, p. 114: "This means that if a system maintained at constant charge is totally surrounded by a dielectric liquid all mechanical forces will drop in the ratio 1/k. A factor 1/k is frequently included in the expression for Coulomb's law to indicate this decrease in force. The physical significance of this reduction of force, which is required by energy considerations, is often somewhat mysterious. It is difficult to see on the basis of a field theory why the interaction between two charges should be dependent upon the nature or condition of the intervening material, and therefore the inclusion of an extra factor 1/k in Coulomb's law lacks a physical explanation." p.115: "Therefore the decrease in force... cannot be explained by electrical forces alone." pp.115-116: "Thus the decrease in force that is experienced between two charges when they are immersed in a dielectric liquid can be understood only by considering the effect of the pressure of the liquid on the charges themselves. In accordance with the philosophy of the action-at-a-distance theory, no change in the purely electrical interaction between the charges takes place."

http://www.amazon.com/Introduction-E.../dp/0763738271
Introduction to Electromagnetic Theory: A Modern Perspective, Tai Chow, p. 267: "Calculations of the forces between charged conductors immersed in a liquid dielectric always show that the force is reduced by the factor K. There is a tendency to think of this as representing a reduction in the electrical forces between the charges on the conductors, as though Coulomb's law for the interaction of two charges should have the dielectric constant included in its denominator. This is incorrect, however. The strictly electric forces between charges on the conductors are not influenced by the presence of the dielectric medium. The medium is polarized, however, and the interaction of the electric field with the polarized medium results in an INCREASED FLUID PRESSURE ON THE CONDUCTORS that reduces the net forces acting on them."

http://farside.ph.utexas.edu/teachin...es/node44.html
"However, in experiments in which a capacitor is submerged in a dielectric liquid the force per unit area exerted by one plate on another is observed to decrease... (...) This apparent paradox can be explained by taking into account the difference in liquid pressure in the field filled space between the plates and the field free region outside the capacitor."

The "perpetual motion machine of the second kind" can be conceived by assuming that the liquid dielectric (water) is alternatively added to and removed from the capacitor-containing system depicted above. Ideally, lifting water to some height and then harnessing it to do work as it falls is a reversible cyclic process that involves zero net work. That is, ideally, we neither gain nor lose work as the liqud dielectric is added to and then removed from the system.

On the other hand, we can draw the capacitor plates together in the absence of the liquid dielectric - the force of attraction works for us - we gain work in the process.

Then we draw the plates apart in the presence of the liquid dielectric and restore the original distance between them. We lose work in the process but this lost work is, for water, 80 times smaller than the work gained when we drew the capacitor plates together in the absence of the dielectric.

Clearly we have a "perpetual motion machine of the second kind" that cyclically and under isothermal conditions converts heat extracted from the surroundings into work.

Pentcho Valev