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A discharge can be ignited and plasma can be sustained when a DC voltage that is delivered to the gas medium via electrodes is higher than the breakdown voltage for the gas. The relationship between this breakdown voltage and the pd product—where p is the gas pressure and d is the distance between the electrodes—is referred to as Paschen's ...
The discharge is taking place in normal atmospheric air, at about 30 kHz, with a discharge gap of about 4 mm. The foot of the discharge is the charge accumulation on the barrier surface. Dielectric-barrier discharge ( DBD ) is the electrical discharge between two electrodes separated by an insulating dielectric barrier. [ 1 ]
Paschen's law is an equation that gives the breakdown voltage, that is, the voltage necessary to start a discharge or electric arc, between two electrodes in a gas as a function of pressure and gap length. [2] [3] It is named after Friedrich Paschen who discovered it empirically in 1889. [4]
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface. Right: The reduction in flux passing through a surface can be visualized by reduction in F or dS equivalently (resolved into components, θ is angle to ...
In a nozzle or other constriction, the discharge coefficient (also known as coefficient of discharge or efflux coefficient) is the ratio of the actual discharge to the ideal discharge, [1] i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.
The equation is also known as the "three-halves-power law" or the Child–Langmuir law. Child originally derived this equation for the case of atomic ions, which have much smaller ratios of their charge to their mass. Irving Langmuir published the application to electron currents in 1913, and extended it to the case of cylindrical cathodes and ...
Surface diffusion is a critically important concept in heterogeneous catalysis, as reaction rates are often dictated by the ability of reactants to "find" each other at a catalyst surface. With increased temperature adsorbed molecules, molecular fragments, atoms, and clusters tend to have much greater mobility (see equation 1).
A-D region: dark discharge; ionisation occurs, current below 10 microamps. F-H region: glow discharge; the plasma emits a faint glow. I-K region: arc discharge; large amounts of radiation produced. A Townsend discharge can be sustained only over a limited range of gas pressure and electric field intensity.