dorsal/arxiv
View SchemaForce on an Asymmetric Capacitor
| Authors | Thomas B. Bahder, Chris Fazi |
|---|---|
| Categories | |
| ArXiv ID | physics/0211001 |
| URL | https://arxiv.org/abs/physics/0211001 |
| Journal | Army Research Laboratory Tech Report No. ARL-TR-3005, June 2003 |
Abstract
When a high voltage (~30 kV) is applied to a capacitor whose electrodes have different physical dimensions, the capacitor experiences a net force toward the smaller electrode (Biefeld-Brown effect). We have verified this effect by building four capacitors of different shapes. The effect may have applications to vehicle propulsion and dielectric pumps. We review the history of this effect briefly through the history of patents by Thomas Townsend Brown. At present, the physical basis for the Biefeld-Brown effect is not understood. The order of magnitude of the net force on the asymmetric capacitor is estimated assuming two different mechanisms of charge conduction between its electrodes: ballistic ionic wind and ionic drift. The calculations indicate that ionic wind is at least three orders of magnitude too small to explain the magnitude of the observed force on the capacitor. The ionic drift transport assumption leads to the correct order of magnitude for the force, however, it is difficult to see how ionic drift enters into the theory. Finally, we present a detailed thermodynamic treatment of the net force on an asymmetric capacitor. In the future, to understand this effect, a detailed theoretical model must be constructed that takes into account plasma effects: ionization of gas (or air) in the high electric field region, charge transport, and resulting dynamic forces on the electrodes. The next series of experiments should determine whether the effect occurs in vacuum, and a careful study should be carried out to determine the dependence of the observed force on gas pressure, gas species and applied voltage.
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"abstract": "When a high voltage (~30 kV) is applied to a capacitor whose electrodes have\ndifferent physical dimensions, the capacitor experiences a net force toward the\nsmaller electrode (Biefeld-Brown effect). We have verified this effect by\nbuilding four capacitors of different shapes. The effect may have applications\nto vehicle propulsion and dielectric pumps. We review the history of this\neffect briefly through the history of patents by Thomas Townsend Brown. At\npresent, the physical basis for the Biefeld-Brown effect is not understood. The\norder of magnitude of the net force on the asymmetric capacitor is estimated\nassuming two different mechanisms of charge conduction between its electrodes:\nballistic ionic wind and ionic drift. The calculations indicate that ionic wind\nis at least three orders of magnitude too small to explain the magnitude of the\nobserved force on the capacitor. The ionic drift transport assumption leads to\nthe correct order of magnitude for the force, however, it is difficult to see\nhow ionic drift enters into the theory. Finally, we present a detailed\nthermodynamic treatment of the net force on an asymmetric capacitor. In the\nfuture, to understand this effect, a detailed theoretical model must be\nconstructed that takes into account plasma effects: ionization of gas (or air)\nin the high electric field region, charge transport, and resulting dynamic\nforces on the electrodes. The next series of experiments should determine\nwhether the effect occurs in vacuum, and a careful study should be carried out\nto determine the dependence of the observed force on gas pressure, gas species\nand applied voltage.",
"arxiv_id": "physics/0211001",
"authors": [
"Thomas B. Bahder",
"Chris Fazi"
],
"categories": [
"physics.hist-ph",
"physics.gen-ph"
],
"journal_ref": "Army Research Laboratory Tech Report No. ARL-TR-3005, June 2003",
"title": "Force on an Asymmetric Capacitor",
"url": "https://arxiv.org/abs/physics/0211001"
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