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Electrical Principles
and Technologies
Science 9
Unit D
1
Topic 1: Energy Conversion
Topic 2: Electrical Technologies
Topic 3: Energy Calculations
Topic 4: Application of Electricity
Topic 5: Alternative Energy Sources
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Topic 1
Energy Conversion:
a) Forms of energy
b) Changing from one to
another
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1a) Forms of Energy
• Chemical – energy stored in chemicals; energy
released through reactions
• Electrical – energy of charged particles; energy
transferred when charged particles (negatively
charged electrons) move from one place to another
• Mechanical – energy within an object due to its
motion or its potential to move
• Thermal – total kinetic energy of the substance;
faster the movement of the particles, higher the
kinetic energy
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1b) Energy Conversions
Energy can appear in many different forms.
For example:
• electrical energy can be converted into light energy (light
bulbs), heat energy (oven), or mechanical energy.
• heat energy (steam), light energy (solar), and mechanical
energy (dams) can also be converted into electrical energy.
•There are many devices that are used to help regulate,
convert, and measure the input energy and the output energy.
ie: Thermocouple, oven, heaters, blender, etc.
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Where does Electricity Come
From?
• Canada’s electricity comes
from:
• 61% hydroelectricity
• 23% steam (from coal)
• 11% nuclear
• 5% burning fossil fuels
• Electrical energy can be
stored in batteries or cells for
later use
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Topic 2
Electrical Technologies:
a)
b)
c)
d)
Static Electricity
Current Electricity
Cells
Circuits
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2a) Static (Unbalanced) Electricity
• Static electricity is a build up of electric charge
on the surface of objects
• If an object builds up electrons, it will have a
negative charge
• If an object loses its electrons, it will have more
protons, therefore it will have a positive charge
• When an electric charge is released, it is called
an electric discharge
• An object is neutral if the number of protons (+)
and number of electrons (-) equal each other 8
• Static electricity occurs when there is a build up of
charge on an object and then it is attracted to an object
of the opposite charge and released quickly; does not
flow.
• This discharge of electricity can result in a spark or if
large enough, a lightning bolt.
• Once the charge has been released the build up of a
new charge must occur for second discharge to happen
again.
•Static electricity occurs best in dry conditions
•500kV Electric Discharge at Power Station
•http://www.youtube.com/watch?v=UVF3iC_voyU
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Electric Charges
All electric charges behave according to the
“Laws of Charges”
There are three “laws” of electric charges
(1) Opposite charges attract each other
(2) Like charges repel each other
(3) Charged objects attract neutral objects
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2b) Current Electricity
• Recall that static electricity is a build up of
electrical charge
• Current electricity is when charged particles flow
steadily from one location to another. However,
this can only occur if the circuit for the flow is
complete.
• Current (I) is measured in the units Amperes (A);
the Ampere is the unit for the rate of flow through
the circuit.
• 1 Ampere = 6.242 x 10^18 electrons passing
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through a point in a second
Current Detectors
There are a variety of devices you can use to detect
current in a wire:
(1) Galvanometer
(2) Used to measure weak or small electric currents
(in Amperes)
• Displays how many electrons are passing through
the wire at a certain point in a set period of time
(2) Ammeter
• Used to measure strong electric currents (rate of
flow)
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2c) Cells
What’s inside a cell?
• There are many
different types; car
batteries, 9 volt
batteries, etc
• A cell is a device that
converts chemical
energy into electrical
energy (produce
chemical-electrical
energy)
• Two cells used
together to produce
electricity is a battery
• All cells contain 2
main parts
(1) Electrodes : metals
which carry electrical
current
(2) Electrolytes:
solutions which
provide
electrical/chemical
electricity
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Dry Cells
• All cells and batteries are sealed with a melted asphalt
or sealing wax to prevent moisture loss
• Inside the seal, exists a container, usually made of zinc
(this acts like a negative pole)
• A carbon rod exists in the middle of the cell, (acting
like a positive pole)
• The container is filled with a paste, made from
different chemicals (electrolyte)
• The zinc container collects electrons, which came from
the carbon rod
• The electrons are then free to move inside the cell to a
conductor (wire)
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Wet Cells
Wet cells use a liquid
electrolyte rather than a
paste-like electrolyte. Wet
cells are common in car
batteries or for electroplating.
In wet cells the two
electrodes are immersed in
the acidic solution
(electrolyte) and then
electrons will move from the
negative electrode to the
positive one, creating a
complete circuit.
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Rechargeable Cells
• Dry and wet cells are called primary cells
because the reaction cannot be reversed
• Rechargeable cells are called secondary
cells because the reaction can be reversed
by an external electrical source; reactants
are restored by the external source, but the
electrodes in the cell will wear out over
time.
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2d) Electric Circuits
• Electrons that pass from a battery through a wire and
then back to the battery travel in an electric circuit
• When there is a flow of electrons through the circuit,
the circuit is closed
• When there is no flow, the circuit is open
• The flow of electrons can be stopped through the use of
a switch
Four main parts to any circuit are:
(1) Control (switch)
(2) Load (the electrical device)
(3) Source (cell)
(4) Conductor (wire)
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Series and Parallel Circuits
• There are two types of circuits:
(1) Series Circuit
• The electrons flow through a device along a single
pathway
• The removal of one electrical device will cause the
entire circuit to stop
• The addition of more electrical devices will
weaken the electrical current
• Example: older Christmas lights
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Series and Parallel Circuits, con’t
(2) Parallel Circuit
• The electrons flow through multiple
pathways
• The removal of one electrical device does
not effect the entire circuit
• The addition of more electrical devices will
not affect the electrical current
• Example: Houses
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Circuit Symbols for Schematic
Diagrams
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Applications for Circuits
• House wiring – parallel circuits
• Microcircuits – contain transistors, resistors
and other components on a really small
scale to control a device
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Switches
• In a circuit, a control must be used to
control the flow of electricity
• A switch is an example of a control
• A switch will open the circuit, thus stopping
the flow of electricity, or close the circuit,
thus starting the flow of electricity
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Conductors and Insulators
• Conductors permit the
easy flow of electrons
• ex. Metal
• Non-conductors
(insulators) prevent the
flow of electrons
• ex. Non-metal
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• In insulators, electrons are tightly bound to
the positive nucleus of their atoms, thus
preventing electricity to flow
• In conductors, electrons move freely away
from the atoms, thus facilitating the flow of
electricity
• Electrons move towards the positive end of
the voltage source
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Superconductors
• Metals such as silver, copper and gold are
excellent conductors, but not perfect
conductors
• Superconductors have no resistance to flow,
thus they are perfect conductors
• Ex. Mercury near absolute zero
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Resistors
• Resistors allow some electron movement, but
provides resistance to it
• As resistance increases, current decreases
• More electrons flow when the resistance is low,
rather than when the resistance is high.
• Resistance is measured in Ohms
• The more resistance, the more energy is released
from the electrical circuit, usually in the form of
heat or light
• A resistor slows the flow of electrons
• ex. Nichrome wire
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Variable Resistors or Rheostat
• Sometimes in a circuit, the flow of
electricity can be changed gradually
• Ex. Dimmer switch
• This type of device is called a variable
resistor, which can increase or decrease the
amount of current flowing through the
circuit.
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Safety Features
• There are many safety features in a properly
wired house-hold:
• At the location of the meter, there are 3
wires:
- 2 Hot wires
- 1 Neutral wire
• These three wires will go to a fuse box,
after passing through the meter
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Neutral and Hot Wires
• The Neutral wire that enters
your home is attached to the
ground, and is not electrically
charged
• The Hot wires that enter your
home are “live” wires, and
are electrically charged
– Hot wires can cause fatal
shocks
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Combining Neutral and Hot Wires
• Because different appliances require different
voltages to operate, the combination of the neutral
and hot wires can provide these differences
1 hot wire + 1 neutral wire = 120 Volts
1 hot wire + 1 hot wire = 240 Volts
• Larger appliances (like stoves and clothes dryers)
need a stronger voltage
• The third prong on a 3 prong plug is a ground wire
used in case of a short circuit.
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Fuses and Circuit Breakers
• Each circuit can only hold a certain amount of
current (too much could cause a fire)
• For safety, fuses and circuits are installed in a
circuit as an “automatic” switch
• If the current becomes too strong, the breaker or
fuse will turn the current off by breaking the circuit
• Fuses contain a small piece of metal that will melt
if the current is too strong
• Circuit Breakers are similar to a fuse except they
are built more like a switch
• Circuits breakers can be reset, where as fuses
cannot
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Topic 3:
Energy Calculations
a) Current
b) Voltage
c) Ohm’s Law
d) Power
e) Energy
f) Efficiency
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3a) Current
•Electric current is also recognized with the symbol, I, and is
measured in Amperes (A).
•Current is the amount of charge that passes a point in a
circuit per second.
•A current can only occur if the circuit is closed (or
completed).
•Amperage is more important to consider than voltage
because 0.001 A has a minimal affect whereas 0.015 can
cause a loss of muscle control and 0.1A can be fatal.
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3a) Current, con’t
• Direct Current (DC) is
when the direction of
current is consistent.
• Alternating Current (AC) is
when the direction of current
switches 60 times/second.
• Can be present in DC
motors and DC generators.
• Can be present in AC motors
and AC generators.
•Used for mp3 players, cell
phones, calculators
•Power companies supply
electricity to homes in the form
of AC
Transformers are used to increase or
decease voltage according to the consumer
needs.
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3b) Voltage
• A volt is a unit in which you
can measure the energy of
charges delivered to a cell
• The more voltage, the more
energy supplied to electrons,
the stronger the electrical
current
• A voltmeter measures voltage
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Voltmeter
• Measures the potential difference between
two points (voltage drop)
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3c) Ohm’s Law
• Ohm was able to determine the relationship
between resistance, current and voltage.
V = IR
V = Voltage, measured in Volts (V)
I = Current, measured in Amperes (A)
R = Resistance, measured in Ohms ()
• Ohm’s Law states that as long as temperature
stays the same:
– The resistance of a conductor stays constant, and
– The current is directly proportional to the voltage
applied
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3d) Power
• Power is the rate at which a device converts
energy
• Measured in Watts (W)
• One Watt equals 1 Joule per second
• For example, 100 Watts means 100 Joules
every second
• The faster a device converts energy, the
higher the power rating
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Calculating Power
P=IxV
• I = Current (Amperes)
• P = Power (Watts)
• V = Voltage (Volts)
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3e) Energy
• Power can be used to calculate the amount
of energy a device uses
• Energy is measured in Joules
E=Pxt
• E = Energy (Joules or Watt·Seconds)
• P = Power (Watts)
• t = Time (s)
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Kilowatt Hours
• Energy produced in the house is too large
over a month to measure in Watts and
Seconds
• Measured instead in Kilowatts (kW) and
Hours (kilowatthours (kWh)
• To find the cost of using energy, multiply
the cost per kilowatt hour by the number of
kilowatt hours used
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Law of Conservation of Energy
• Law states that energy cannot be created or
destroyed only converted from one form to
another
• Every time energy is converted from one form to
another, energy is always converted to useless
forms of energy (like heat)
• The energy that is input into the system will
always be greater than the useful energy that
comes out of the system
• NO device is 100% efficient
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3f) Energy Efficiency
• To figure out how good a system is at converting
energy from one form to another, scientists
calculate the systems efficiency
Efficiency = Output /Input x 100
• Remember output will always be less than input
• Energy is measured in Joules
• Efficiency is measured in percent, as it is the ratio
of useful energy that comes out of a device to total
energy that went in
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Increasing Efficiency
• Efficiency is lost due to friction which
results in energy being transformed into a
thermal form
• To increase efficiency, need to decrease
friction
• Try to insulate a device so it does not lose
heat; add a capacitor to store some of the
electrical energy
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Topic 4:
Applications of Electricity
a) Magnetism
b) Motors
c) Generators
d) Transformers
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4a) Magnets
There are basically 2 types of magnet:
(1) Permanent:
• often made from hard
steel alloy
• has two poles: North and
South
• North and South poles
never change
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4a) Magnets, con’t
And, the second type:
(2) Electromagnet:
• made from a coil of wire
attached to a source of
current
• when current runs through
wire, the wire has magnetic
effects
• North and South poles
switch depending on which
way the current is flowing
• Becomes stronger if a
stronger current is running
through the wires or with49
more coil
Magnets, con’t
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4b) Motors
• Motors depend on both
electromagnets and permanent
magnets to create mechanical
energy from electrical energy
• Mechanical energy can be used to
run all sorts of electrical devices
(i.e. blenders, hairblowers..)
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Parts of a Motor
• Power Source: Wires connect the motor to the
source of electrical energy (generator, battery)
• Brushes: Metal Pieces that conduct electrical
energy from the source to the commutator
• Commutator: Attached to the axle and the
armature, the commutator rotates; as the it
turns, the axle turns
The commutator is responsible for reversing the
flow of electrons in the wires, when the gaps are
not in contact with the metal brushes, thus
changing the direction of the current
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Parts of a Motor, con’t
• Permanent Magnets: responsible for pushing the
electromagnet (armature) due to the repulsion between
the electromagnet and the permanent magnet
• Armature: shaft that rotates with the coil wrapped
around it
• Electromagnet: Armature spins due to the repulsion
between the electromagnet and the permanent magnet,
spinning the axle
• Axle: Metal rod that uses mechanical energy to
perform a specific function
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54
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How a Motor Works
• The wires conduct electricity to the brushes, which
leads to the commutator
• As long as the metal brushes are in contact with the
metal portion of the commutator, the electrical current
flows in the right direction
• When the current flows down the armature, the
electromagnet becomes magnetized and repels off of
the permanent magnets
• When the brushes come in contact with the gaps, the
current stops and reverses, changing the poles on the
electromagnet
• This causes the electromagnet to repel again, away from
the permanent magnets, thus continuing the spinning 55
cycle
• watch?v=it_27NdKgmY
56
4c) Generators
• Generators use the same electromagnetpermanent magnet concept as motors, but
instead of using electrical energy to spin the
armature, mechanical energy spins it
• This spinning creates a current, thus producing
electrical energy; therefore mechanical energy
is creating electrical energy.
• DC generator very similar to a DC motor
• AC generator uses a loop of wire attached to
two slip rings which switch the current as the
loops move through the magnetic field
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4d) Transformers
• Used to change the amount of voltage with
very little energy loss.
• Current is transmitted at a high voltage over
a long distance and then is reduced to a
useable form when it reaches its destination
• There are step-up transformers (increase
voltage) and step-down transformers
(decrease voltage)
58
Topic 5:
What are they and why are
they important?
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Alternative
Electrical
Energy
Sources
•Are sources of renewable
energy forms.
•Are not commonly practiced or
considered unconventional .
• Ex: solar, wind, biomass,
geothermal, tides
Conventional
Energy
Sources
•Are sources of nonrenewable or more
commonly practiced
renewable energy forms.
•Are commonly used
around the world
•Ex: hydro, fossil fuels
(coal, oil, gas), nuclear
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Why alternate energy sources are
important.
• Existing energy forms are non-renewable and will disappear.
•Alternate sources may be better for the environment and
ecosystem in the long run.
•Alternate sources utilize forms that can be reused and
recycled.
•Alternate sources may be cheaper in the future, after
expensive start-up costs.
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