Charging by Friction
Charging by friction produces many
of the same effects produced by
static electricity.
Examples:
Drying clothes in a dryer
- The tumbling motion is kind of a
rubbing action
Walking across a carpet
- The friction between the carpet and
persons shoes produces a charge on both
the person and the carpet.
Rubbing a comb through your hair
- The comb strips electrons from your
hair and becomes more negative while
your hair will become more positive
The electrostatic series is a list to
determine the kind of electric charge
produced on each substance when any two
substances on the list are rubbed
together.
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Charge by Contact
A single spark produced by a charge
transferred by contact can cause dangerous
fires and explosions.
When charging by contact occurs, one
object is already electrically charged. The
other object may or may not be charged as
well. The important thing to remember is
that for charge by contact to occur, there
has to be a difference in the amount of
charge already on the two objects.
*Hand touching door-handle example*
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Charge by Induction
For this type of electric charge to occur,
there doesn‛t actually have to be any
contact between either object.
Remember: ANY neutrally charged object
that comes in contact with a charged
object will be attracted to that object.
The same works for induction, except they
don‛t touch.
Example: The dust particle
If it comes by, but does not touch, a
charged particle, it will push the opposite
charge towards the side nearest the
charged particle. This will mean that one
side of the dust particle will be negatively
charged, while the other side will be
positively charged.
-----
-+
--- +++
Charged
substance
++
++
++
Dust particle with
evenly spread out
charges
+ ++
+
++
----
-+- +++
If it has nowhere to go (neutral object
not touching anything), the charge will
evenly spread back out over the neutral
object when the charged object is
removed.
This charging effect is known as induced charge
separation.
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Insulators
An electrical insulator is a substance
in which electrons cannot move freely
from atom to atom.
If atoms of an insulator build up a
positive or negative charge, they stay
on that atom and attract other
neutral or oppositely charged
particles.
Examples: wood, paper, plastic,
rubber, silk
Title: Nov 22­5:53 PM (9 of 11)
Conductors
A conductor is a substance in
which electrons can move freely
from one atom to another.
Examples: silver, copper, gold, aluminum
Discharging
If a charged object has all of the excess
electric charges removed, it is said to be
discharged, or neutralized.
The simplest way to discharge any object
is to bring it in contact with the Earth.
This is called grounding.
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Pith Ball Lab
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