Electrical Conductors and Insulators
Battery
Lamp
Test terminals
In this presentation you will:
 identify electrical conductors and insulators
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Sunday, March 17, 13
Introduction
Electrical
conductors are
materials that
allow electric
current to flow.
Lamp
Battery
Typical conductive
materials include
silver, copper, and
steel.
Test
terminals
Copper
Silver
Sunday, March 17, 13
Steel
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Introduction
Electrical insulators are
materials that do not allow
electric current to flow.
Plastic
Typical insulator materials
include plastic, wood, and
ceramic.
Materials have different levels
of conduction or insulation.
For example, silver and steel
are both conductors, but silver
is a better conductor.
Sunday, March 17, 13
Wood
Ceramic
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Atomic Structure
All materials are made from atoms.
We can model the appearance
of an atom by having a central
nucleus made of protons and
neutrons.
Electrons, which have a tiny
electrical charge, move around the
central nucleus in orbits.
Each orbit can have a maximum number of
electrons.
By knowing how many electrons there are, you
can work out their distribution.
Sunday, March 17, 13
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Atomic Structure
An electron remains in orbit around the nucleus
because it is oppositely charged to the nucleus.
“Unlike charges attract,
like charges repel“
-Law of Charges.
The further out the
orbit is, the weaker the
force holding the
electron in place.
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The outermost electron(s) may be very
weakly bound to an atom.
Sunday, March 17, 13
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+
+
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Electrons in Atoms
Atoms are very close to each other in a solid, so it is
quite common for an electron in an outer orbit to
move to a neighbor’s outer orbit if there is space.
If an electron leaves an outer
orbit, it leaves a space behind.
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The atom now has an overall
positive charge, and it will
quickly attract an electron in to
fill the space.
In some solids, electrons are
moving between atoms all the time.
Sunday, March 17, 13
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Conduction in Solids
If a source of
electromotive force (EMF),
such as a battery, is
connected across a solid,
all electrons will now be
under the influence of an
external field.
If the field is strong enough,
any loosely bound electrons
will start to move toward the
positive battery terminal.
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Sunday, March 17, 13
Conduction in Solids
The loosely bound
electrons may well be
captured by atoms as they
pass, but if they are only
loosely held, they could be
released again.
Materials that are classed as
good conductors will easily
allow the movement of these
free electrons.
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Sunday, March 17, 13
Question 1
Why is silver a very good electrical conductor?
A) It stops electrons from moving between atoms
B) It allows electrons to move easily between atoms
C) It is shiny
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Sunday, March 17, 13
Question 1
Why is silver a very good electrical conductor?
A) It stops electrons from moving between atoms
B) It allows electrons to move easily between atoms
C) It is shiny
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Sunday, March 17, 13
Insulators
Resistance is the opposite
of conductance.
Materials that are good
conductors of electricity
have a low resistance.
Silver
Materials that are poor
conductors of electricity
have a high resistance.
Plastic
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Sunday, March 17, 13
Insulators
If we look at the atomic
structure of metals that
are good conductors, we
see that each has only a
single electron in the
outermost orbit.
In addition, this outer electron
is relatively easy to remove.
Materials that are good
insulators do not have a single
free electron in the outermost
orbit, therefore, have a high
resistance.
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Conductor - silver
Single
electron
in silver
atom
structure
Insulator - phosphorus
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Question 2
Which atomic structure would produce the best
insulator?
A)
C)
B)
D)
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Sunday, March 17, 13
Question 2
Which atomic structure would produce the best
insulator?
A)
C)
B)
D)
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Sunday, March 17, 13
Uses of Conductors and Insulators
Conductors are used in
applications where we
want electricity to flow,
for example, in power
cables.
Insulators are used in
applications where we
need to be protected
from possible contact
with electricity, for
example, the shielding
around cables.
Insulator
Conductor
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Sunday, March 17, 13
Electrocution!
Providing a conduction pathway
for electricity can be fatal.
The human body is made
mostly of water and is an
electrical conductor, although a
poor one.
Many people have died by becoming the
conduction pathway between an
electricity supply and the ground.
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Sunday, March 17, 13
Electrocution!
Even though air is a
poor electrical
conductor, if the voltage
is high enough, lightning
will cause a conduction
pathway for electricity to
flow to the ground.
Some tall buildings have
lightning conductors to
deliberately channel the
electricity safely to the ground.
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Sunday, March 17, 13
Question 3
Which of the following items need to be
manufactured from electrically insulating material to
help prevent electrocution?
A) The plug cover on a desk lamp powered by an
electrical outlet
B) The case of a hair dryer
C) The motor cover of a desk fan
D) All of the above
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Sunday, March 17, 13
Question 3
Which of the following items need to be
manufactured from electrically insulating material to
help prevent electrocution?
A) The plug cover on a desk lamp powered by an
electrical outlet
B) The case of a hair dryer
C) The motor cover of a desk fan
D) All of the above
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Sunday, March 17, 13
Summary
In this presentation you have seen:
 what makes a material an electrical conductor or
insulator
 examples of electrical conductors and insulators
End >
Sunday, March 17, 13