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A water drop with an electrical charge opposite to that of the water surface below will be either attracted permanently or repelled, depending upon the strength of the force pulling the two together. Two oppositely charged liquids normally are attracted toward each, as can be seen in the upper row of images. But when the attraction between them passes a certain critical point, the drop of liquid will no longer be able to merge with the surface. Though still attracted, its attraction will be short-lasting. The drop's behavior will resemble that of a bouncing ball. Image courtesy Ristenpart et al 2009 |
Opposites attract - but they may not stay togetherOpposites may always attract. But they may not remain together long-term. In a counter-intuitive discovery published in the current edition of the journal Nature, researchers from Harvard, the University of California at Davis, Princeton, and Penn State University report that oppositely charged drops of water will not attract permanently, but instead will bounce off each other indefinitely when subjected to a force of attraction created by what physicists call an electric field that is too strong. |
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