Static Charge
-and-
Van de Graaff Generators
What is Static Charge?
Here, we're talking about charge as the difference in the
number of electrons that two different objects have. When
the atoms of one object give up or lose their electrons, these
electrons end up somewhere else. Another object picks up or
gains these strays. Since electrons are negatively charged,
and protons are positively charged, an object that has picked
up electrons without picking up protons will have a negative
charge overall.
The electron got it’s name when a scientist
noticed particles clinging to what material
after he rubbed it with rabbit’s fur?
(Hint: Its Greek translation is ‘elektron’)
a. rubber
b. amber
c. iron
d. aluminium
When two objects made of very different materials are rubbed
together, one will be more likely to give away its electrons.
The other will be more likely to accept these electrons. The
more you rub, the more electrons jump from one to the other.
How do you know it is there?
Lightening is a large-scale example of
electrons jumping from one place to another.
Where does the extra build up of electrons
come from?
a. Rain droplets collide with each other as they
fall, knocking off electrons
b. As layers of air of different temperatures rub
together, the cooler layer donates electrons
c. Pockets of rising moisture lose electrons when
hit by falling ice and sleet
d. Clouds bump into each other, knocking off
electrons
Once an object has gained electrons, it will want
to return to its neutral state and have just as
many protons as electrons. If enough electrons
jump from your skin to another object at once
you can feel a shock, hear a zap, or see a small
spark.
Many times, however, the charge built up is too
small for humans to notice without help. A tool
called a voltmeter can measure how many more
electrons are on object than are on its neighbour.
Where can you find it?
Large build-ups of electrons can give away their
presence in other ways. Since similar charges repel
each other and opposite charges attract, you can see
negatively charged objects repelling each other and
clinging to positively charged objects.
Number the items below from most likely to
donate electrons (1) to most likely to accept
electrons (7)
If you stick two pieces of tape to a smooth surface,
then quickly peel each off, the electrons on the nonsticky sides of the tape will try repel each other
If you slide down a plastic playground slide quickly
in cotton clothing, the negative charges on your hair
will repel each other and your hair will stick up.
(For best results, make sure the air is dry)
Fur
Van de Graaff generator
The Van de Graaff generator was invented by Robert J. Van de Graaff in 1929 at Princeton
University. One of the largest can generate 2 million volts (XX electrons) and uses metal spheres
that are each 15 feet across.
Van de graff generators come in all sorts of sizes and can use similar materials to get the
same job done. They can produce anywhere from (number) to (number)!
http://www.engr.uky.edu/~gedney/courses/ee468/expmnt/vdg-graph.gif