Presentation for Junior Level
Students
Learning outcomes:
- An
atom is the basic building block for everything. It is made of protons
(positive charge), electrons (negative charge), and neutrons (no charge)
- I
will emphasize on the protons (example: basketballs) which are big and stable
as well as electrons (tennis balls) which are smaller and mobile
- The
Bohr model is much like planets orbiting the sun (with the protons being the
sun and electrons orbiting around it)
-
Illustrate
with boy / girl analogy (when two boys or girls come together, they repel one
another; when a boy and a girl come together, they attract)
-
Let
us start off with an atom that has 3 basketballs and 3 tennis balls. If we
steal some tennis balls, what happens? The atom becomes positively charged
which will now attract to tennis balls from other neutral atoms
-
Glass
rod and Silk cloth demo (explained in the Apparatus section under Demo #1)
-
Comb
and Hair demo (explained in the Apparatus section under Demo #2)
-
The
fundamental principle behind this apparatus is separating opposite charges at
both ends of the rubber belt
-
Materials
(explained in the “How to Build a Van De Graff Generator” section)
-
Due
to difference in materials, the belt strips electrons from the dome and
transfers it to the bottom. So what happens to the dome? There are now
excessive basketballs spread out all over its surface
-
When
we touch the generator, tennis balls in our bodies want to attract to the
basketballs spread out over the dome. This leaves us positively charged. We are
now a part of the generator and the belt is basically stripping electrons from
us instead
-
Our
hair is originally neutral, but the tennis balls move away upon contact. Since
there are mostly basketballs left on each strand of hair, the like charges will
repel each other (making our hair stand up)
-
Hair
raising demo (explained in the Apparatus section under Demo #3)
-
Electric
spark demo (explained in the Apparatus section under Demo #4)
-
The
same principle of static electricity applies when we feel a shock upon touching
a metal doorknob on a dry winter day