Project 4
Static Electricity
These effects are caused by electricity. We call this
static electricity
because the electrical charges are
not moving, although pulling clothes apart sounds like
static on a radio. When electricity is moving (usually
through wires) to do something in another place, we
call it an
electric current
.
Electricity
is an attraction and repulsion of particles in
a material. All materials are made up of
atoms
, which
are really, really tiny. Atoms have a nucleus (which has
positive electrical charges), which is surrounded by tiny
electrons
(negative electrical charges). When you rub
a material, electrons can move on or off the atoms, giv-
ing them an electrical charge.
Electricity exists everywhere, but is so well balanced,
that you seldom notice it. But, sometimes differences
in electrical charges build up between materials, and
sparks can fly. Lightning is the same effect as the
sparks between clothes, but on a much greater scale.
A cloud holds static electricity just like a sweater.
Photo courtesy of: NOAA Photo Library, NOAA Central Library;
OAR/ERL/National Severe Storms Laboratory (NSSL) [via pingnews].
Why do
you often “see”
lightning before
you “hear” it? It is
because light trav-
els faster than
sound.
+
+ +
+
+
Electrons
–
–
–
–
–
–
Nucleus
This diagram shows the
structure of an atom, except
that the nucleus and elec-
trons are actually much far-
ther apart.
Find some clothes that cling together in
the dryer, and try to uncling them.
Rub a sweater (wool is best) and see how
it clings to other clothes.
Take off a sweater (wool is best) and listen
for crackling noises. Try it in a dark room
and see if you see sparks. Compare the
effects with different fabrics (wool, cotton,
etc.).
Note:
This project works best on a cold dry day. If
the weather is humid, the water vapor in the air al-
lows the static electric charge to dissipate, and this
project may not work.
If you wet the clothes then the static charge should
mostly dissipate. (Try it.)
You need a comb (or plastic ruler) and a
water faucet for this part. Run the comb
through your hair several times then hold it
next to a slow, thin stream of water from a
faucet. The water will bend towards it. You
can also use a plastic ruler. Rub it on your
clothes (wool works best).
Rubbing the comb
through your hair
builds up a static
electrical charge on
it, which attracts the
water.
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