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The equivalent series resistance of polypropylene capacitors has been determined under rated voltage, in the range 1 kHz–1 MHz, between 220 K and 370 K by a calorimetric technique. The original feature of this determination of capacitor losses lies in the use of the isothermal calorimetry and in the measurement of an electrical power and not of a temperature increase. The frequency dependence of the equivalent series resistance, at various temperatures, enables to separate the losses in the conducting material from those in the dielectric and to get their respective variations as a function of frequency and temperature. These variations of the equivalent series resistance with frequency at a given temperature have been reproduced by using an equivalent circuit composed of resistors, inductors and capacitors. This model has been verified for non-sinusoidal waveforms such as those met with in a filtering circuit and is used to evaluate by simulation the losses of the capacitor.

The time dependence of the surface potential of an insulating material is theoretically investigated in the case of simultaneous surface and volume ohmic conduction. When the material presents a constant surface conductivity, the first part of the decrease with time of the surface potential is strongly influenced by the initial distribution of charges and cannot be used to determine the surface conductivity. On the other hand, at rather long times after the surface has been charged, the potential of the surface follows an exponential variation with time, the expression of the corresponding time constant is given in different cases. This model is found in good agreement with experiments performed with photo-oxidized epoxy resins placed in a humid atmosphere.

The electrical conduction of purified aromatic liquids in the tip-plane electrode geometry was studied for high electric fields. The current voltage curves, the current pulses were measured for dc applied voltage in toluene, benzyltoluene, and in the saturated hydrocarbon ndecane. In n-decane, current pulses are similar to corona discharges in electronegative gases and to pulses previously studied in liquid cyclohexane. In aromatic liquids, a discontinuity in the current-voltage curve was also observed for an electric field of 4.5±0.5 MV.cm -1 whereas current pulses were detected for higher fields. This behavior is attributed to the ionization and electronic attachment of aromatic molecules

La conduction de solutions d'électrolytes dans le cyclohexane a été étudiée entre électrodes recouvertes de films d'alumine ou de polyphénylène-oxyde lors de l'application d'un échelon de tension continue. L'injection faible observée aux temps courts dans les solutions de TlAPi a les mêmes caractéristiques qu'entre électrodes métalliques nues (même variation avec le champ, avec la conductivité de la solution). Les ions injectés sont les ions de l'électrolyte, ils sont créés dans la zone de force-image. Aux temps longs le film qui bloque les ions du liquide, devient un injecteur très fort d'ions dans le liquide. La nature de ces ions n'a pas été déterminée.