One of the most important kinds of energy in the modern technological
world is electrical energy. Electric currents turn motors and
drive machinery. Electric currents provide the energy of laborsaving
applicances such as electric mixers, power drills, vacuum cleaners,
and automatic dishwashers. Clearly, the currents possess energy.
Electrical energy is linked with the basic structure of the
atom. According to modern atomic theory an atom has a heavy, positively
charged center called the nucleus. One or more light, negatively
charged electrons circulate around the nucleus. The
positive nucleus and the negative electrons attract one another.
This attraction keeps most of the electrons circulating near the
nucleus. But sometimes a neighboring nucleus will also attract
the electrons of the first atom. This is how a chemical bond is
formed. So, in a way, all chemical energy is a special, microscopic
kind of electrical energy.
Metals are made up of atoms that contain many electrons. Because
of the peculiar structure of metal atoms, the atomic nuclei are
not strong enough to hold on to all their electrons.
Some of the electrons more or less float from nucleus to nucleus.
These free electrons can take part in an electric current.
Work must be done to separate positive and negative charges
if one is to produce a surplus of electrons in one place and nuclei
that are missing one or more electrons at another place. When
this situation occurs, as in a battery, energy is stored. If one
end of a metal wire is connected to the place where excess electrons
are collected (the negative terminal on a battery) and the other
end of the wire is connected to the place where excess nuclei
are collected (the positive terminal on a battery), the electrons
of the wire flow to join the nuclei. Electrons farther down the
wire flow after the first electrons, and the electrons from the
battery move into the wire. This total electron flow from the
negative terminal of the battery through the wire and into the
positive terminal is called an electric current.
