Why Batteries Deliver a Fairly Constant Voltage until Dead

• DOI: 10.1021/ed200211s
• Publication Date: 2012-08-06T17:41:18Z
• Authors: Garon C. Smith; Md. Mainul Hossain; Patrick MacCarthy
• Keywords: Galvanic cell; Constant (computer programming); Constant voltage; Plot (graphics); Constant current

Two characteristics of batteries, their delivery nearly constant voltage and rapid failure, are explained through a visual examination the Nernst equation. Galvanic cells described in detail: (1) wet cell involving iron copper salts (2) mercury oxide dry cell. A complete description requires three-dimensional surface because potential is function two variables: activities both oxidized reduced forms each redox couple. Dry potentials, which utilize solid or pure liquid species, functions only one variable can be by pair traces traditional plot. Plots relatively flat for most activities, but they exhibit cliffs under extreme conditions. The spots responsible fairly that batteries deliver; explain why fail so quickly.