When opposite charges repel - physics-math - 17 September 2009 - New Scientist
OPPOSITES always attract, right? Not quite. A new experiment has shown that a drop of water with positive electrical charge can be made to "bounce off" a negatively charged object.
William Ristenpart of the University of California at Davis accidentally applied a strong electric field to a beaker filled with oil and water. At first the mixture erupted into a turbulent mess, but as he turned down the voltage Ristenpart saw droplets of waterMovie Camera suspended in the oil bouncing between the electrode at the top of the beaker and the oil-water boundary below. The droplets were positively charged, so why didn't they merge with the negatively charged body of water?
Ristenpart thinks that positive ions drain out of the droplet and
negative electrons come in through the bridge, so the droplet, now
negatively charged, is drawn up to the positive electrode, where it
regains its original positive charge, and so on.
