Back discharge

As the bodies are separated the potential difference will increase. However, the potential difference at any separation will be directly proportional to the respective value of k. Since this will not vary markedly, the potential difference between the bodies will not increase very much as they are separated. Therefore, since contact potentials are normally considerably below ionization potentials, it is unlikely that back discharge will actually occur owing to air ionization. However, from Table VI and Eq. (47) it is also apparent that the maximum surface gradient may be of the order of 108 V/cm (if = IV and separation distance is lA), which should be enough to cause field emission and discharge by this means. 

Thus the amount of back discharge cannot be readily calculated. It would seem unlikely, however, that the potential difference would drop below the contact potential as the bodies are separated. This would mean that the actual charge leaking off would be only a small fraction of that originally present. 

It seems fortuitous that the same order of maximum charge levels has been reported for metal-metal contacts as for insulator-insulator contacts. This might indicate that back discharge could be a controlling factor in establishing final charge levels. 

The favorable influence of moisture is apparently due to two effects (311). Moisture reduces the sparking tendency between a point and a plate, or in any similar electrode system, and also decreases the resistivity of the precipitated catalyst. The lower resistivity eliminates back discharge, a condition that results in abnormal power consumption and loss of efficiency. 

The energy input into a CO2 laser is in the form of an electrical discharge through the mixture of gases. The cavity may be sealed, in which case a little water vapour must be added in order to convert back to CO2 any CO which is formed. More commonly, longitudinal or, preferably, transverse gas flow through the cavity is used. The CO2 laser can operate in a CW or pulsed mode, with power up to 1 kW possible in the CW mode. 

At the cathode, water molecules are discharged yielding gas and hydroxide ions, OH. Some of the caustic generated in the cathode compartment back-migrates to the anode compartment and reacts with dissolved chlorine (Cl2, ) to form chlorate as follows... 

Ammonia has low miscibility in mineral oils, alkylbenzenes, and polyol ester lubricants, particularly at low temperatures. A typical ammonia system uses a coalescing separator that removes all oil in droplet or aerosol form and drains it back to the compressor. Sometimes separators are equipped with some means of cooling the discharge gas to condense any oil that is discharged as a vapor. 

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