Electrical Fruit Power

Circa 1991


Question:  A student in 7th grade is interested in "Electrical Fruit."
Can an experiment be designed to see if current can be
produced through fruit? Can a fruit be used in place of a
battery? If so, can a comparison be set up vs. battery power?
---------------------------------------
I found a couple of very brief articles in the "Journal of Chemical
Education", one from Feb.  1988, the other from Feb.  1992.  The earlier
one is titled "A Homemade Lemon Battery".  It claims that, using a
galvanized nail and a penny for the two "terminals", you can get a
potential difference of about 1 volt from a lemon.  This article describes
a classroom demo where several "lemon batteries" in series, along with
a capacitor to accumulate charge, were used to set off a flash cube.
The other article, titled "A Lemon-Powered Clock", claims that a series
pair of lemon batteries can be used to power a quartz watch (the authors
say you can get only 0.6 - 0.7 volt from a lemon battery.) They claim
that you can do this with oranges and potatoes as well.  I wonder if
apples would also work -- they contain a very weak acid called malic acid.
This article says that, besides copper and zinc (the galvanized nail),
magnesium and iron may be used for the two metal terminals.  Another book
I looked in suggests that you roll the lemons between your hands before
using them; I presume that this is to release more lemon juice from the
tissues.

rcwinther
====================================================================