All matter is made up of atoms, which in turn
are made up of smaller particles. The three main
particles that make up an atom are protons,
neutrons, and electrons. Protons have a
positive charge and are contained in the nucleus
of an atom along with the neutrally charged
neutrons. The electrons, which are negatively
charged, move around the positively charged
nucleus. In some types of atoms, like in a metal,
the electrons are only loosely bound to the
nucleus and can easily be displaced and move about
the other atoms. The flow of of these
electrons is what we call a current of
For electricity to be useful, we need a net
flow of electrons to travel in one direction. To
do this, we complete a circuit (a closed path for
the electrons to move around) and apply an
electric potential that drives the electrons to
move in one direction.
So where can we get electricity?
Electricity is the flow of energy from one
place to another. One simple way is by
chemical reaction. This is what happens in
batteries. The chemicals in a battery react
together and can produce an electrical charge.
When the battery is placed into a circuit, we get
a current of electricity (or the flow of energy!)
that can be used to power whatever device it is
hooked up to.
Electricity involves a field of physics called
electromagnetism. As you might be able to tell
from carefully looking at the word,
electromagnetism involves the relation between
electric and magnetic fields. What this means is
that a electrical current can induce a magnetic
field around it, and a moving magnetic field can
induce a electric field! For example, if you had
a piece of wire and began flowing a (relatively
high) current through it, you could actually
measure a magnetic field around the wire, i.e., if
you placed a compass close to the wire, you would
no longer be reading the earth's magnetic field,
but rather the induced field from the wire!
A similar case also exists in that moving
magnetic fields can induce electrical currents.
It is the relative motion between the two that is
important, so either a conducting wire can be
moved through a stationary magnetic field, or a
magnet can be moved near a stationary conducting
wire. Can you think of ways in which
electricity can be generated using the relative
motion between magnets and conducting wire? What
kind of natural energy sources could we use to
cause motion of either magnets or wires relative
to each other?