mere touch of a switch.
What is the nature of this unseen phenomenon? This
question cannot be answered, because the exact nature of electricity is not known.
However, the uses, effects, and laws governing electrical action are well
understood, and so these known characteristics will be described here.
b. The Nature of Matter. To study electricity, you must understand something
about the constitution of matter.
The smallest particle of matter that still
retains the identity of the material being studied is the molecule. Every molecule
is made up of atoms, which are the smallest amount of an element capable of
entering into a chemical combination.
The atom can be further subdivided into
particles classified as protons, electrons, and neutrons.
Protons are positively
charged particles which, together with neutrons, are found in the nucleus of the
The neutrons have no electrical charge.
The negatively charged electrons
move in orbits around the nucleus.
It is the study of the action of these
negatively charged particles that concerns you in the study of electricity and
(1) Figure 1 shows the diagram of the helium atom and its parts. Since all
elements are made up of a different number of electrons, protons, and
neutrons, we may assume that the difference between the various
elements is in the number of electrons, protons, and neutrons each
element has, and in how these parts are arranged.
The helium atom.
(2) In some elements, the electrons rotate about the nucleus in different
numbers of orbits.
It is found that electrons in the outer orbit of
some elements are easier to move from one atom to the next than in
It is the movement of these electrons that we call
electric current, or simply current.
a. Current. Electrons rotate about a nucleus continually in all matter, but
in doing so they neither work nor produce any of the effects of electricity. To
produce an electrical effect, either some of these electrons must be removed from
the atom, or the electrons in a conducting medium must be caused to move from one
atom to another in a particular direction.
The rate at which electrons move is
called current, which is measured in amperes.