GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Electrical conductivity. A circuit consisting of a battery, light bulb and two electrodes in a beaker is used to illustrate electrical conductivity. When the beaker is filled with water, the bulb does not light up because pure water is a very poor conductor. When table salt (sodium chloride, NaCl) is added to water, it dissociates into Na+ and Cl- ions that carry electric charges in the solution and the bulb lights up (this photo 3). When sugar is added to water, it dissolves but does not form ions, so the solution does not conduct electricity and the bulb does not light up as in Photo 2 of 3.
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