Related Experiment Video
Updated: Jul 18, 2026
10:03
The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids
Published on: September 30, 2014
Theory for formation of a low-pressure, current-free double layer
1Space Plasma, Power and Propulsion, Research School of Physical Sciences and Engineering, Australian National University, ACT 0200, Australia.
Physical Review Letters
|August 16, 2006
Summary
A new theory explains how current-free double layers form in low-pressure plasma devices. Particle balance and ionization determine double layer potential, which disappears at very low or high pressures.
Area of Science:
- Plasma physics
- Low-pressure discharges
- Double layer formation
Background:
- Current-free double layers are crucial in plasma devices.
- Understanding their formation mechanism is essential for plasma control.
Purpose of the Study:
- Develop a diffusion-controlled theory for current-free double layer formation.
- Investigate the influence of pressure on double layer stability.
Main Methods:
- Theoretical modeling of a low-pressure plasma system.
- Analysis of particle dynamics including thermal ions, accelerated ions, and electrons.
- Formulation of particle balance equations.
Main Results:
- The upstream particle balance determines the double layer potential.
- Double layers disappear at very low pressures due to ionization imbalance.
- Energy relaxation processes cause disappearance at higher pressures.
Conclusions:
- The developed theory accurately predicts double layer behavior.
- Pressure is a critical factor controlling double layer existence and potential.
- The findings align with experimental observations in plasma sources.
Related Concept Videos
01:02Fluid Pressure over Flat Plate of Variable Width
When a flat plate is submerged in a fluid, the fluid exerts pressure on the plate. This pressure can lead to many different phenomena, including drag and buoyancy. To understand the behavior of the fluid over a flat plate of variable width, it is essential to analyze the distribution of the pressure exerted.
The pressure distribution on the plate can be calculated by determining the force that acts on a differential area strip of the plate. Thus, the magnitude of the force is equal to the...
The pressure distribution on the plate can be calculated by determining the force that acts on a differential area strip of the plate. Thus, the magnitude of the force is equal to the...
01:13Excess Pressure Inside a Drop and a Bubble
The shape of a small drop of liquid can be considered spherical, neglecting the effect of gravity. This drop can further be considered as two equal hemispherical drops put together due to surface tension. The forces acting on the spherical drop are due to the pressure of the liquid inside the drop, the pressure due to air outside the drop, and the force due to the surface tension acting on the two hemispherical drops.
01:30The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
01:17Steady, Laminar Flow Between Parallel Plates
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.
01:22Couette Flow
Couette flow represents the flow of fluid between two parallel plates, with one plate fixed and the other moving with a constant velocity. This configuration allows for a simplified analysis using the Navier-Stokes equations, which govern fluid motion under conditions of viscosity and incompressibility. For Couette flow, the assumptions include a steady, laminar, incompressible flow with a zero-pressure gradient in the flow direction. This flow type is beneficial for understanding shear-driven...
01:18Boundary Layer Characteristics
When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This phenomenon is characterized by a thin region adjacent to the surface where viscous forces dominate, influencing the fluid's velocity profile. The development of the boundary layer begins at the leading edge of the surface and evolves as the fluid moves downstream.As the fluid flows over the surface, friction between the fluid and the wall slows down...