Galvanic Cell
Definition
A battery: a device that turns a spontaneous chemical reaction into electric current.
Technical definition
A galvanic (voltaic) cell is an electrochemical cell in which a spontaneous redox reaction drives electrons through an external circuit, converting chemical energy to electrical energy. The anode is negative and the cathode positive.
Example
The Daniell cell, zinc in zinc sulfate and copper in copper sulfate connected by a salt bridge, produces about 1.10 V from the spontaneous Zn + Cu^2+ reaction.
Common confusion
Galvanic and electrolytic cells are opposites. Galvanic cells PRODUCE electricity from spontaneous reactions, while electrolytic cells CONSUME electricity to force nonspontaneous reactions.