Moving electric field effect on dielectric/gas

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SUMMARY

The discussion centers on the effects of a moving electric field on a dielectric medium, specifically in a gas-filled pipe. It explores whether the polarization induced by the electric field can create a drag force on the gas, similar to mechanical blades. Key equations mentioned include the momentum balance equation and the equation of state, which are essential for analyzing the interaction between the electric field and the gas. The conversation concludes that the motion of the dielectric edge in a parallel plate capacitor is crucial for understanding the force dynamics involved.

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  • Understanding of electric field dynamics and polarization in dielectrics
  • Familiarity with fluid dynamics and momentum balance equations
  • Knowledge of thermodynamics, particularly the equation of state
  • Basic principles of electrostatics and energy calculations
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Physicists, electrical engineers, and researchers in fluid dynamics and electrostatics who are interested in the interaction between electric fields and gaseous media.

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So I was wondering, can a moving electric field produce a drag force on gas for example similar to that which would result from physical blades moving the gas.

Electric field applied to a dielectric if not as strong as to produce breakdown produces polarization. I wonder can this polarization create a drag on the dielectric medium if the electric field moves in time and space.

For a simple example think of a pipe filled with gas, take two wires charged to a high potential and located at the sides of the pipe, the pipe itself is of such material as to allow the E field lines to pass through, surely it would attenuate the field but for the sake of argument suppose it doesn't.
So we drag the two charged wires along the length of the pipe, what would be the effect on the gas within the pipe?

My own idea is that either the polarization from the field passes along the gas but in such a way that each next segment is simply being polarized without any drag on it or the previously polarized segment tends to be pulled along and so creates a push on the gas in front of it creating drag.?thanks.
 
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There's a classic problem that asks you to calculate the force required to pull a dieletric out of a parallel plate capacitor. The key is the motion of the edge of the dielectric slab, since that determines what percent of the field sees a polarizable medium and what percent sees vacuum.

In the case of the gas in the pipe, you will also need to factor in the equation of state and momentum balance: $$\rho \frac{D\vec{u}}{Dt} = -\nabla p - (\vec{P} \cdot \nabla) \vec{E} = 0$$ $$ k_B T \nabla n = -(\vec{P} \cdot \nabla) \vec{E}$$ where ##p## is the pressure, ##\vec{P}## is the polarization density, and ##\frac{D\vec{u}}{Dt}## is the material derivative of fluid velocity (zero in this case, because we're assuming steady state) where in the last bit I made the assumption that the wires are moving slowly enough that the gas is in thermal equilibrium. From this you can solve for the density, and thus the susceptibility everywhere in the gas. From there you can find the electrostatic energy, and then calculate the electrostatic energy, and lastly the force by taking the derivative of the electrostatic energy with respect to the wires' positions.
 
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I have a common plasma globe with blue streamers and orange pads at both ends. The orange light is emitted by neon and the blue light is presumably emitted by argon and xenon. Why are the streamers blue while the pads at both ends are orange? A plasma globe's electric field is strong near the central electrode, decreasing with distance, so I would not expect the orange color at both ends.

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