Current Electricity – moving electrons
Static Electricity – electrons waiting to be moved
What part of the atom is removable?
Electrons
can move
from one
atom to
another
Atoms become charged by gaining or
losing ...
Electrons
Electrons move from
atom to atom
Electric charges
can be
transferred by
three ways
3 ways to transfer electric
charge
•Conduction
•Induction
•Friction
Conduction
Excess electrons pass to a neutral object
when touched
Induction
Electrons transferred when a neutral object
is near a charged object (in the electric
field)
Friction
moving electrons by force
LAW OF ELECTRIC CHARGES
Like charges
REPEL
-+
-+
+ Opposite charges ATTRACT --
Objectives for the Day
Explain the three ways electrons can be
transferred.
Identify the type of electron transfer in given
scenario.
Static Electricity
What Is Static
Electricity?
A stationary electrical
charge that is built up on
the surface of a material
Where do charges come from?
Matter is made up of atoms.
+
–
neutron (neutral)
+
+
–
Proton (positive charge)
+
–
atom
–
electron (negative charge)
nucleus
Where do charges come from?
If electrons = protons
neutral
If electrons > protons
 negative charge
(gains electrons)
If electrons < protons
 positive charge
(loses electrons)
Where do charges come from?
When a balloon rubs a piece of wool...
–
–
–
–
–
–
wool
+
+
+
+
+
electrons are pulled from the
wool to the balloon.
The balloon has more electrons than
usual.
The balloon: – charged,
The wool: +charged
Insulators
Insulators: materials that do NOT
allow electrons to flow through
them easily.
Insulators can be easily charged by friction as the extra
electrons gained CANNOT easily escape.
Conductors
Conductors: materials that allow
electrons to flow through them easily.
Conductors CANNOT be easily charged by friction as
the extra electrons gained can easily escape.
Where do charges come from?
Rubbing materials does NOT create
electric charges. It just transfers
electrons from one material to the other.
Conductors and Insulators
Conductors
Insulators
Copper
Aluminum
Humans
Water
Most metals
Rubber
Cloth
Hair
Plastic
Glass
Paper
Electro-negativity
+++++
++++
+++
++
+
Relative
electro-negativity
ranking for some
common materials
from electron donating
materials (+, glass) to -electron accepting
--materials (-, teflon)
--------
•
•
•
•
•
•
•
•
•
•
•
•
Glass
Human Hair
Nylon
Silk
Fur
Aluminum
Paper
Cotton
Copper
Rubber
PVC
Teflon
Induction: The charge is created by an electric field
When a negatively charged rod is put near a metal can...
- - - - - - -
electrons of the can are pushed
away from the rod.
attraction  top of the can: positive
bottom of the can: negative
++ +
metal
can
+
+
-
-
-
-
repulsion
A balloon has a negative charge
when rubbed by a woollen cloth.
1
If the balloon can attract some paper scraps, which of the
following cannot be the charge of paper scraps?
A
Neutral
C
Negative
B
Positive
A balloon has a negative charge
when rubbed by woollen cloth.
2
During rubbing, what have been transferred between the
woollen cloth and the balloon?
A
Electrons
C
Neutrons
B
Protons
Static Discovery Lab:
Data Analysis
Activity
Example:
Plasma Ball
Type of Electron
Transfer
Support for the answer
Induction
Light bulb lit up without
touching the plasma ball
Grounding
What is grounding?
An object is grounded when it is connected
to the earth.
Using a conductor to move an
electric charge to the ground.
Grounding
b How does grounding occur?
+
+
+ +
+
When we touch a metal sphere
of positive charge...
electrons flow from the
earth to the metal to
neutralize the metal.
Metal becomes neutral.
Grounding
How does grounding occur?
–
–
– –
–
Similarly, if the metal is of
negative charge...
extra electrons flow
from the metal to the
earth and the metal
becomes neutral.
Discharge
Electric Discharge
The release of
built up electrons