Static Electricity
It has been known
for centuries that
when dissimilar
substances are
rubbed together,
they often become
“charged” with the
ability to attract and
repel other objects.
Charging Objects
For example: When an ebonite rod is
rubbed on animal fur, both the rod and the
fur become charged electrically.
Electric Charges
There are two kinds of electric
charge: positive and negative.
Electric charges can exert
forces upon each other.
Unlike charges attract
each other.
Like charges repel.
Static Electricity
Benjamin Franklin (17061790) was the first person
to assign the plus and
minus signs to electric
charges.
Franklin was also the first
to infer (correctly) that only
one kind of charge needs
to move in order to explain
everything.
Static Electricity
All matter is made of atoms, which in turn are
made out of electrically charged particles.
So why don't we
notice static electric
effects all of the
time?
Static Electricity
All matter is made of atoms, which in turn are
made out of electrically charged particles.
So why don't we
notice static electric
effects all of the
time?
Because ordinarily,
atoms have equal
amounts of positive
and negative charge!
Static Electricity
But when objects are rubbed together, the
electrons are easily stripped out of the atoms.
When a glass rod is
rubbed on silk, electrons
are rubbed out of the
atoms in the glass
(making appear to be
positive) and are rubbed
on to the silk (making it
appear to be negative.)
Charging by Contact
When a charged object touches an uncharged
object, the uncharged object acquires the same
kind of charge that the charged object had.
Polarization of Charge
When a negatively
charged balloon
approaches a wall, the
negative charges on the
balloon repel negative
charges in the wall away
from the surface.
The positive charges
left on the surface
attract the negatives on the balloon, making the
balloon stick to the wall.
You explain it!
Why will you get
a slight shock
from the
doorknob after
scuffing your feet
across the
carpet?