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ERIC Number: EJ1003030
Record Type: Journal
Publication Date: 2012-Nov
Pages: 5
Abstractor: As Provided
Reference Count: 17
ISSN: ISSN-0021-9584
Why Batteries Deliver a Fairly Constant Voltage until Dead
Smith, Garon C.; Hossain, Md. Mainul; MacCarthy, Patrick
Journal of Chemical Education, v89 n11 p1416-1420 Nov 2012
Two characteristics of batteries, their delivery of nearly constant voltage and their rapid failure, are explained through a visual examination of the Nernst equation. Two Galvanic cells are described in detail: (1) a wet cell involving iron and copper salts and (2) a mercury oxide dry cell. A complete description of the wet cell requires a three-dimensional Nernst surface because the potential is a function of two variables: the activities of both the oxidized and reduced forms in each redox couple. Dry cell potentials, which utilize solid or pure liquid species, are functions of only one variable and can be described by a pair of traces in a traditional plot. Plots of the Nernst potential are relatively flat for most activities, but they exhibit cliffs under extreme conditions. The flat spots are responsible for the fairly constant voltage that batteries deliver; the cliffs explain why batteries fail so quickly. (Contains 7 figures.)
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A