| A voltaic cell harnesses the electrical work of a spontaneous chemical reaction to power a lightbulb. The zinc and copper strips act as electrodes, and the salt bridge (in this case potassium chloride) allows electrons to flow between the beakers without allowing the solutions to mix. When the circuit joining the two systems is completed (as shown on the right), the reaction generates electric current. Note that metal from the zinc strip is used up (oxidation), and the strip appears eaten away. The copper strip is built-up as additional electrons react with the copper sulfate solution to produce additional metal (reduction). Replacing the lightbulb with a battery would reverse the reaction, creating an electrolytic cell. |
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