In a nutshell, a battery uses a chemical reaction to produce an electrical current.
In this experiment, we will create an electric current using nothing more than our
own bodies (Reeko promises this won't hurt.... much).
- Mount the copper and aluminum metal plates to two separate pieces of wood.
- Connect one plate to one of the DC microammeter's terminals using an alligator clip
and the hookup wire. Connect the other plate to the second terminal.
A DC microammeter, which is an instrument that measures the electric current in
a circuit, can be purchased from your local Radio Shack store.
- Now place one hand on each plate.
You should see an electric current generated on the meter. If you don't see
a reading then simply reverse the connections. If you still don't see a reading
then you may need to clean the metal plates (or get a pair of better reading glasses).
When you place your hands on the metal plates, a thin film of sweat on your hands
acts just like the acid in a battery, producing a chemical reaction with the copper
plate and a chemical reaction with the aluminum plate. Your hand actually
takes negatively charged electrons away from the copper plate (leaving positive
charges behind) and gives electrons to the aluminum plate (causing it to become
negatively charged). This difference in charges produces an electrical current
which flows through the meter.
- Wet both hands.
- Once again, place one hand on each plate.
Metals are very efficient at this electrical current we have created. Your
body resists the flow of current (through the skin). When you wet your hands
you greatly decrease the resistance and thus increase the current giving you a higher
reading on the meter.
Parent's Note. Batterys have actually been around a lot longer than
you'd think. The first practical battery was probably developed by Count Alessandro
Volta, an Italian scientist, in the late 1790's. Volta's invention became known
as a voltaic pile. It consisted of a stack of pairs of silver and zinc disks. The
pairs were separated from one another by disks of cardboard moistened with a salt
In 1836, John F. Daniell, an English chemist, introduced a more efficient primary
cell. The Daniell cell had two liquid electrolytes and produced a steadier current
than Volta's device. In 1859, the French physicist Gaston Plante invented the first
secondary battery, the lead-acid storage battery. During the 1860's, another French
scientist, Georges Leclanche, invented a type of primary cell from which the modern
dry cell was developed.
Through the years, scientists have designed smaller but increasingly powerful batteries
for the growing number of portable electric devices. For example, a lithium cell
is so tiny that it is often called a button battery. But it produces voltages higher
than any other single cell. It uses lithium metal as the negative electrode and
any one of several oxidizing agents as the positive electrode. Lithium cells are
used mainly in calculators, cameras, pacemakers, and watches.