Electricity is not just something you buy in a battery. It
is one of the basic ingredients of the Universe. Everything around us is made
of invisible atoms, and the atoms contain particles that carry electric charge.
Charge can be positive or negative. Particles with the same kind of charge
repel each other, while opposite charges attract. When charges move, we
get CURRENT ELECTRICITY, which drives much of the modern
world.
Electricity is a basic force of nature, and lightning shows how
powerful it is. Lightning happens when strong air currents tear apart positive
and negative electrical charges. This creates huge tension, eventually released
as a giant spark caused by STATIC ELECTRICITY. Electricity can
destroy and kill, but engineers can tame its wild power to light whole
cities.
Everything in the Universe is made of atoms, and atoms are held
together by electricity. In an atom, negatively charged electrons swarm around
a positively charged nucleus. A positive charge attracts a negative charge, so
electrons rarely escape the pull of the nucleus. As the charges cancel each
other out, the atom as a whole has no electric charge.
We rarely notice the electricity all around us, because
positive and negative charges usually balance. However, when objects touch,
electrons can hop between them. This may leave each object with a static
charge. A comb, for example, can strip electrons from hair, making the hair
positively charged, crackly, and fly-away.
Charged objects are attracted to uncharged objects. This effect
(electrostatic induction) is used in paint spraying. The object to be painted
is connected to the ground so it stays uncharged. A spraygun charges the paint,
and electrostatic induction pulls the paint onto the object so that every bit
gets painted, even the back.
Static electricity depends on electrons not being able
move around easily, so that charge builds up in one place. But in some
materials – mostly metals – electrons can move freely to form an
electric current. An electric current is measured by the amount of charge
passing a fixed point each second. In most currents, the electrons move more
slowly than a snail.
At a rock concert, huge quantities of electricity are controlled
by tiny electric currents in microphones to produce deafening sound.
Electricity is also used to make lights blaze, and cameras turn the light into
electrical signals to create giant images of the musicians above the stage. The
whole show is run by electronic computers.
When electrons jostle their way through a metal, such as copper,
they make the metal hot. The metal may even melt. This could be a disaster, but
not when the process is used for joining metal parts by welding. In welding, a
rod connected to a low-voltage supply of electricity is touched on to the metal
parts that need joining. A brilliant electric arc forms as the tip of the rod
is vaporized (turned into gas), and the parts join. Arc welding even works
under water, to build and repair pipelines and oil rigs.
