Transcript PSAA Curriculum

PSAA Curriculum
Unit Physical Science Systems
Problem Area
Energy and Power Systems
Controlling Electrical
Current: Circuits,
Conductors, and
Insulators
Lesson
Identify the various materials
used in these cords/cables.
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What are these materials?
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What are they mainly used for?
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Are they good insulators or conductors? Why?
Learning Objectives
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Explain electricity and how electricity
flows along a complete circuit.
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Describe the components of a complete
electrical circuit.
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Explain the functions of conductors and
insulators and identify common
conductors and insulators used in
agricultural facilities.
Terms
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Alternating current
Circuit
Complete circuit
Conductor
Current
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Direct current
Electricity
Insulators
Semiconductors
How is electrical energy
controlled?
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Electricity is a flow of electrons along a
conductor.
The conductor is the path along which the
electrons flow.
For such a flow to exist, it is necessary that
there be a complete circuit.
The complete circuit must allow for the
electricity to flow from the source to the load
and back to the source.
Conductors
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A conductor is a piece of metal in the form of a
wire.
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Metals are excellent conductors of electricity.
Circuit
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The circuit is a path for electrons to move
through components and wires.
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Electrons moving in a negative to a positive
direction along a conductor is current.
Currents
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Direct current flows in one direction only,
from source to load.
Alternating current involves a change in
direction by the electrons, occurring at a rate
of 60 times per second or 60 hertz.
All residences in the United States use
alternating current in their circuits.
What is necessary for a complete
electrical circuit?
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To have an electrical circuit, there must be a
source of applied power, a load to which the
power is applied, a path for the electrons to
pass from the source to the load, and a return
path for the electrons to pass from the load to
the source.
What is necessary for a complete
electrical circuit?
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A switch is used as a means to control the
electron flow.
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Overcurrent protection in the form of a fuse or
circuit breaker is added for safety.
What is an insulator and a
conductor and what determines if a
substance is an insulator or a
conductor? What is a
semiconductor?
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All materials may be classified as either
conductors of electricity, non-conductors of
electricity (insulators), or partial (semi)
conductors of electricity.
Insulators & Conductors…
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Atoms of conductors give up electrons
resulting in electron flow.
By surrounding a conductor with an insulator
electron flow can be controlled and used.
Insulators are non-conducting material lacking
a sufficient supply of free electrons to allow
for movement of current through the material.
Semiconductors
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Semiconductors have resistivity values
between those of insulators and conductors.
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Silicon is an example of a semiconductor.
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The electrons in semiconductors are bound
more strongly than in conductors, but less
strongly than in insulators.
Semiconductors (cont.)
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The electrical properties of semiconductors
can be controlled by adding other elements to
alter their structure and change their electrical
properties.
These altered semiconductors are the basis of
all modern electronic circuits.
Semiconductors are used to make transistors,
integrated circuits, and chips for
microelectronics.
Common insulation materials,
cables, and flexible cords used in
electrical wiring
Common insulation materials,
cables, and flexible cords used in
electrical wiring
Review/Summary
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How is electrical energy controlled?
What is necessary for a complete electrical
circuit?
What is an insulator and a conductor and what
determines if a substance is an insulator or a
conductor?
What is a semiconductor?