Download Unit A: Biological Diversity

Unit D: Electrical Principles and Technologies
STS and Knowledge:
1. Investigate and interpret the use of devices to convert various forms of energy to electrical energy,
and electrical energy to other forms of energy
SF
pp.294,296,297
SIA pp.81,319321
identify, describe and interpret examples of mechanical, chemical, thermal
(heat) and electrical energy
SF
pp.293,294,296,
297
SIA pp.321-324
investigate and describe evidence of energy transfer and transformation
(e.g.,mechanical energy transformed into electrical energy, electrical energy
transferred through power grids, chemical energy converted to electrical
energy and then to light energy in a flashlight, thermal energy converted to
electrical energy in a thermocouple)
 An electric motor is a device that used to turn something. It converts
electrical energy to mechanical energy.
 A generator is a device that produces electricity. It converts mechanical
energy to electrical energy.
 A thermocouple is a device that produces electricity. It converts thermal
energy to electrical energy.
 A cell / battery is a device that produces electricity. It converts chemical
energy to electrical energy.
There are two main types of energy: kinetic and potential. Kinetic energy is the
energy of motion. Any object or particle that is moving has kinetic energy.
Potential energy is stored energy. Any object or particle that has energy but is
not using it has potential energy. The unit of energy is the Joule (J).
 mechanical energy- the combined total of kinetic and potential energies
of an object or particle
 chemical energy- a type of potential energy; the energy stored in the
bonds of molecules
 thermal energy- a type of kinetic energy; the energy of vibrating
particles in a material
 electrical energy- a type of potential energy; the energy carried by
charged particles
A team of students constructed a solar powered car for their science fair project.
The car was made by hooking up the car assembly to a motor and a solar panel.
During the initial test-drive, the car traveled across the length of a well-lit room.
This car converted:
a. solar energy into mechanical energy into electrical energy
b. solar energy into potential energy into wind energy
c. solar energy into electrical energy into mechanical energy
d. solar energy into thermal energy into chemical energy
SF pp.301-308
SIA pp.288-292
investigate and evaluate the use of different chemicals, chemical
concentrations and designs for electrical storage cells (e.g., build and test
different forms of wet cells)
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Electrochemical cell: a package of chemicals designed to produce small
amounts of electricity e.g. a battery.
Dry cell- a device that converts chemical energy to electrical energy. They
consist of two electrodes (two different pieces of metal) and an electrolyte (a
conducting solution). Charges leave the negative electrode, pass through the
electrolyte, and return to the positive electrode. They are called dry cells
because the electrolyte is in the form of a paste.
Wet cell- Same as above, but the electrolyte is a liquid that is usually an acid.
Dry cells and wet cells. Figures 1.20 and 1.21 Science in Action 9
Dry cells and wet cells are both examples of primary cells. The reaction cannot
be reversed, and as a result, the cells can only be used once.
Rechargeable cells are known as secondary cells. Two examples of
rechargeable cells are Ni-Cd and Nickel metal-hydride.
Jack made a list of facts about a typical electrochemical cell.
Fact A: cell converts electrical energy to chemical energy
Fact B: cell consists of 2 different metal electrodes and an electrolyte
Fact C: a D cell, like the ones used in flashlights, is classified as a wet cell
Fact D: a cell with copper and zinc has good electrodes
SF pp.314
SIA pp.325
If the statement is true, place a 1 in the corresponding blank. If it false, place a 2.
______ ______ ______ ______
A
B
C
D
construct, use and evaluate devices for transforming mechanical energy into
electrical energy and for transforming electrical energy into mechanical
energy
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Figure 3.10 Science in Action 9
Electric motors
By winding current-carrying wire into a coil and wrapping it around an iron core,
you can make an electromagnet. An electromagnet will move to line up with the
magnetic field of a nearby permanent magnet. To keep the electromagnet
spinning, motors use a commutator (split ring) and brushes. The commutator
breaks the connection of the coil and thus the magnetic force. The armature
continues to spin because of momentum. The commutator then reconnects!
Figure 3.17 Science in Action 9
Electric generators
A generator works in reverse. Instead of pumping an electric current into the
armature and the armature turning as a result, you turn the armature and current
is generated as a result.
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SF pp.317
SIA pp.
modify the design of an electrical device, and observe and evaluate resulting
changes (e.g.,investigate the effect of changes in the orientation and placement
of magnets, commutator and armature in a St. Louis motor or in a personallybuilt model of a motor)
Several ways to change the speed at which the armature in a motor spins:
a) increasing the strength of the magnets increases the speed of the armature
b) increasing the current increases the speed of the armature
c) increasing the number of coils of wire between the magnets increases the
speed of the armature
d) changing the orientation of the magnets so that like poles are against each
other will stop the armature
Jose has produced an electric motor for his science class. He wants to make the
motor spin faster without using more voltage. He can do this by:
a. increasing the number of turns of wire
b. decreasing the strength of the fixed side magnets
c. making more splits in the commutator
d. changing to a power supply with more electrical output
2. Describe technologies for transfer and control of electrical energy
SF pp.330-331
SIA pp.284-288
assess the potential danger of electrical devices, by referring to the voltage
and current rating (amperage) of the devices; and distinguish between safe
and unsafe activities
The voltage is the energy of individual charges. Ultimately it is the total energy
that provides the danger, so a high voltage does not present a significant danger
if there are not a lot of charges (low current). It becomes dangerous when the
current (number of charges per second) is also increased to a high level,
providing more overall energy.
To assess the danger of an electrical device, check the manufacturer’s label for
voltage and current rating. Remember that it is the combination of high voltage
and high current that provides the danger.
Some electrical safety pointers*:
 Never handle electrical devices when you are wet or near water unless they
are specially designed and approved for use in wet areas.
 Don’t use any power cord that is frayed or broken.
 Always unplug electrical devices before looking inside or servicing them.
 Don’t put anything into an electrical outlet other than proper plugs for
electrical devices.
 Don’t overload circuits by plugging in and operating too many devices.
 Stay away from power lines.
 Don’t bypass safety features built into home wiring, appliances, and other
electrical devices.
 When unplugging a device, pull on the plug, not on the electrical cord.
 Never remove the third prong from a three-prong plug.
*Science in Action 9 (Addison Wesley) p.285
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SF pp.266-268
SIA pp.274-278
distinguish between static and current electricity, and identify example
evidence of each
Static electricity- the build-up of electric charges (protons and electrons are not
equal!). Charged objects cause charge separation when they are brought close
to neutral objects.
e.g. the build-up of charges in your hair when you put a wool
sweater on; these charges are transferred from the wool to
your hair
e.g. lightening results from a build-up of charges in clouds;
when the build-up becomes to large, the charges jump
(discharge) to the ground
Current electricity- the flow of electric charges; the more charges that flow per
second, the higher the current. In general, electrical current
carries electrical potential energy which is used to operate
electrical devices
e.g. electrical energy carrying charges flow through a light
bulb; the electrical energy from the charges is converted to
light and heat
Two balloons became charged by rubbing them with different cloth materials.
+ - - + + - +
Balloon A
SF pp.269
SIA pp.298
- + - + + + Balloon B
What happens if Balloon A and Balloon B are
brought near to each other?
a. Balloon A will attract Balloon B
b. Balloon A will repel Balloon B
c. Balloon A will have to effect on Balloon B
d. Balloon A will fuse with Balloon B
identify electrical conductors and insulators, and compare the resistance of
different materials to electric flow (e.g., compare the resistance of copper
wire and nickel chromium/Nichrome wire; investigate the conduction of
electricity through different solutions; investigate applications of electrical
resistance in polygraph or lie detector tests)
Electrical conductor- a material that allows charges to flow through it; some
materials are better conductors that others in that they allow
charges to flow easier
e.g. most metals are good conductors; copper is a very good
conductor and is used to carry charges through your
house, while nichrome metal conducts charges but not
as well.
Superconductor – have almost no resistance to electron flow.
Eg. Mercury at absolute zero.
Resistance-the property of something that hinders the motion of electric charge
and converts electric energy into other forms of energy such as light,
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heat, and sound. The symbol for resistance is the letter R and the units
are Ohms ().
e.g. the filament in a light bulb generates heat because of resistance
e.g distilled water is a resistor
e.g. lie detectors – measures skin resistance because sweat is a salty and
conductive solution
Electrical insulator- a material that does not allow charges to flow through it;
insulators offer resistance to the flow of electric charge. If
something is a good insulator, it is a poor conductor.
e.g. rubber and plastic are good insulators
Michelle constructed a circuit in her science
class.
Different objects were tested to determine
whether they would complete the circuit to
make the bulb light. The objects tested were:
i. a glass rod
ii. aluminum foil
iii. a paper clip
iv. a plastic spoon
SF pp.273,283
SIA pp.298-302
Michelle concluded that the bulb will light for:
a. i and ii
b. i and iv
c. ii and iii
d. ii and iv
use switches and resistors to control electrical flow, and predict the effects
of these and other devices in given applications (e.g., investigate and describe
the operation of a rheostat)
switch- something that will start or stop electric current
resistor- something that has resistance; something that resists the flow of electric
charge and takes electrical potential energy from charges and converts
it to some other type of energy, such as light, heat, sound, etc.
rheostat- a resistor whose resistance value can be changed. Since nichrome wire
has a relatively high resistance, adding more nichrome to a circuit will
increase the overall resistance. Taking nichrome away will decrease
the overall resistance. (aka variable resistor)
Mary and Sam created a motorized windmill for their science class using a series
circuit. However, they found that their windmill moved too fast! They could
adjust the speed of the windmill by:
a. adding another battery to the circuit
b. creating a parallel circuit
c. adding a light bulb to the circuit
d. removing the switch from the circuit
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SF pp.278
SIA pp.304-305
describe, using models, the nature of electrical current; and explain the
relationship among current, resistance and voltage (e.g., use a hydro-flow
model to explain current, resistance and voltage)
voltage- the energy of each individual charge. The symbol for voltage is the
letter V and the units are Volts (V). Volts are measured with a voltmeter.
Pretend an electric circuit is a race track. Each car represents a charge. Each car
has a certain amount of gasoline that provides its energy. The gasoline that each
car has would represent the voltage. The number of cars that pass by the starting
line every second would represent the current. As cars (charges) go up hills
(resistors), each one of them uses up gasoline (voltage). Each car needs to get
more gasoline (voltage) at the pit stop (battery).
Jason and Celine used a sports cartoon to show how current, resistance, and
voltage are related.
Person 1 is
pushing to the
right
Person 2 is holding
person 1 back
From this model, it can be concluded that X, Y and Z represent
a. current, voltage and resistance
b. voltage, resistance and current
c. voltage, current and resistance
d. current, resistance and voltage
SF pp.281-282
SIA pp.306-307
measure voltages and amperages in circuits, and calculate resistance using
Ohm’s law (e.g., determine the resistance in a circuit with a dry cell and
miniature light; determine the resistances of copper, nickelchromium/Nichrome wire, pencil leads and salt solution) [Note: At this level,
students are not required to use Ohm’s law to calculate current flow.]
Amperage- a measurement of the strength of electric current. The symbol for
amperage is the letter I and the units are Amps (A). Amperage is
measured with an ammeter. Smaller currents are measured with
galvanometers.
Ohm’s law provides for the relationship between voltage across a resistor (the
energy that each charge loses across the resistor), the current through the resistor
(the amount of charges that are flowing through the resistor each second), and
the resistance of the resistor. Ohm’s law can be written as a mathematical
equation:
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V
I
e.g. An electric dryer draws an electric current of 22 A. The voltage drawn by
the dryer is 220 V. What is the resistance of the dryer?
R
Given: I=22 A
Find: R = ?
R
SF pp.286
SIA pp.307-309
V=220 V
V 220V

 10
I
22 A
Marie-Frédéric had a problem. When she plugged a 1 000 W curling iron and a
1200 W hair dryer into the same 110 V outlet, the circuit breaker tripped. She
had overloaded the circuit that was rated 12 A. How many amperes of current
over the safe limit was she?
a. 4
b. 6
c. 8
d. 10
develop, test and troubleshoot circuit designs for a variety of specific
purposes, based on low voltage circuits (e.g., develop and test a device that is
activated by a photoelectric cell; develop a model hoist that will lift a load to a
given level, then stop and release its load; test and evaluate the use of series
and parallel circuits for wiring a set of lights)
-8-
A photoelectric cell uses light to emit electrons. These electrons can go around
an electric circuit and power devices.
The above burglar alarm uses a beam of UV light to cause electrons to be
emitted from the photoelectric cell, causing the iron to become magnetized. This
magnetized iron attracts the switch from the second circuit, breaking that circuit,
preventing the alarm from sounding.
When the burglar breaks the beam of UV light, no electrons flow in the first
circuit so the iron loses its magnetism. The switch from the second circuit falls
closed, completing the second circuit, causing the alarm to sound.
SF pp.273
SIA pp.311-313
investigate toys, models and household appliances; and draw circuit
diagrams to show the flow of electricity through them (e.g., safely dismantle
discarded devices, such as heating devices or motorized toys, and draw
diagrams to show the loads, conductors and switching mechanisms)
An electrical circuit is a system made up of 4 subsystems:
1. Source – cell or battery
2. Conductor – wire
3. Control – switch
4. Load – lamp/motor
The following is a list of symbols used when drawing electric circuit diagrams
(from Science in Action 9 (Addison-Wesley) p.312
A series circuit is when the current passes through each load in the circuit. In a
series circuit there is only one path for the current to pass through.
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Figure 2.24 from Science in Action (Addison-Wesley) p.313
A parallel circuit has more than one path, so current does not necessarily pass
through each load. In this case, it one path is broken there is still at least one
other path for current to come through.
Figure 2.25 from Science in Action (Addisson-Wesley) p.313
A circuit was constructed according to the following diagram:
S1
L3
L2
L1
L5
S2
L4
Conditions to be met:
1. L1 is burnt out
2. S1 is closed
3. S2 is open
SF pp.322
SIA pp.315
If the 3 conditions were to be followed on this circuit, which lamps would
continue to light?
a. only L2
b. L2 and L3
c. L2, L3 and L4
d. L2, L3 and L5
identify similarities and differences between microelectronic circuits and
circuits in a house (e.g., compare switches in a house with transistors in a
microcircuit)
The similarity between household circuits and microelectronic circuits is that
they perform the same basic function: to power an electrical device.
The primary difference between household circuits and microelectronic circuits
is the scale. Household circuits are on a much bigger scale. In a typical house,
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you might have dozens of electrical components. On a typical microelectronic
(integrated circuit), there may be millions of transistors and resistors.
A transistor is often referred to as a solid state component with no moving parts.
Transistors are found in microcircuits and function as a:
a. load
b. conductor
c. switch
d. source of power
3. Identify and estimate energy inputs and outputs for example devices and systems, and evaluate the
efficiency of energy conversions.
SF pp.328
SIA pp.
identify the forms of energy inputs and outputs in a device or system
e.g. lightbulb- the input energy is electrical, the output energy is light and heat.
e.g. cd player- the input energy is electrical, the output energy is sound (and also
kinetic as the disc spins)
SF pp.323-324
SIA pp.332,333
apply appropriate units, measures and devices in determining and
describing quantities of energy transformed by an electrical device (e.g.,
measure amperage and voltage, and calculate the number of watts consumed
by an electrical device, using the formula P = IV [power (in watts) = current
(in amps) voltage (in volts)]; calculate the quantity of electric energy, in
joules, transformed by an electrical device, using the formula E = P t [energy
(in joules) = power (in watts) time (in seconds)])
power- the rate at which a device converts energy. The symbol is P and the units
are Watts (W). 1 Watt is equal to 1.0 J/s.
There are two equations that describe power relationships:
P  IV
E  Pt
e.g. A 100 W light bulb is plugged into a 120 V outlet and is on for 5 minutes.
a) What is the current?
Given:
P=100 W
V=120 V
t=5 minutes=300 seconds
Find:
P  IV  I 
P 100W

 0.83 A
V 120V
I=?
b) What the energy used?
Find: E=?
E  Pt  (100W )(300s )  30000 J
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250 kJ of energy is added to a container of water heated by an 800 W hot plate
for 6 minutes. How much heat energy is given off by the hot plate?
a. 800 J
b. 48 000 J
c. 288 000 J
d. 480 000 J
SF pp.328-329
SIA pp.335
apply the concepts of conservation of energy and efficiency to the analysis of
energy devices (e.g., identify examples of energy dissipation in the form of
heat, and describe the effect of these losses on useful energy output)
The law of conservation of energy states that energy cannot be created or
destroyed, but that it can be transformed from one type to another.
Efficiency refers to the percentage of original energy (input) that remains after
an energy conversion (output). No device is 100% efficient. This does not mean
that energy is destroyed; it was simply converted to an unusable form such as
heat.
e.g. A light bulb uses electrical energy input to produce light. The conversion is
not 100% efficient. Some of the energy was lost in the form of heat. Note that
no energy was destroyed!!
SF pp.328-329
SIA pp.336-338
compare energy inputs and outputs of a device, and calculate its efficiency
(e.g., compare the number of joules of energy used with the number of joules
of work produced, given information on electrical consumption and work
output of a motor-driven device)
The equation that describes energy efficiency is as follows:
% Efficiency 
useful _ energy _ output
x100%
total _ energy _ input
e.g. A light bulb uses 780 J of electric energy, but produces only 31 J of light
energy. What is the efficiency of the light bulb?
Given:
Useful energy output=31 J
Total energy input=780 J
Find: % Efficiency= ?
% Efficiency 
useful _ energy _ output
31J
x100% 
x100%  3.9%
total _ energy _ input
780 J
250 kJ of energy is added to a container of water heated by an 800 W hot plate
for 6 minutes. What is the efficiency of this heating set up?
a. 87%
b. 0.87%
c. 115 %
d. 0.09%
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SF pp.
SIA pp.339-343
investigate and describe techniques for reducing waste of energy in common
household devices (e.g., by eliminating sources of friction in mechanical
components, using more efficient forms of lighting, reducing overuse of
appliances as in “overdrying” of clothes)





pick appliances that are energy efficient (they have energy labels on them)
don’t leave lights on when not in the room
use full loads of laundry and dishes
improve bearings and lubricants in devices to reduce friction
add more insulation around stoves, refrigerators, and walls
4. Describe and discuss the societal and environmental implications of the use of electrical energy.
SF pp.340-342
SIA pp.345-350
identify and evaluate alternative sources of electrical energy, including oil,
gas, coal, biomass, wind, waves and batteries (e.g., identify renewable and
nonrenewable sources for generating electricity; evaluate the use of batteries
as an alternative to internal combustion engines)
Renewable source- a source of energy that can replenished naturally in a
relatively short period of time
Examples of renewable sources:
 Tides- moving water from tides turn turbines that run generators
There are not a lot of tidal power stations in the world because of the
difficulty in finding a suitable location. They are, however, an
environmentally friendly source of energy. Hydro-electric plants like
those near Niagra Falls, capture the energy of falling water.

Wind- use the wind to turn a turbine that run generators
Modern windmills are more efficient than older ones because of the
propeller shaped blades. They are not particularly efficient, but are
environmentally friendly. They are usually grouped together in wind
farms, such those in Pincher Creek.

Sunlight- uses the Sun to generate electricity
Recall that when a photoelectric cell can emit electrons when exposed
to light. Sunlight can be used to generate electricity in this way.
Modern silicon materials have made sunlight a more efficient way of
producing current. Solar cells are now used in many applications,
including calculators and spacecraft and the International Space
Station. This source of electricity is very environmentally friendly.

Batteries – Convenient source of electricity for portable devices, but they
only produce energy after being charged using electricity from an external
source. They actually use more energy than they produce!
Non-renewable source- a source of energy that cannot be replenished naturally
in a relatively short period of time.
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
Fossil fuels- coal, oil, and natural gas.
Fossil fuels are a reasonable choice in areas that have a large deposit
that is easy to excavate. Mining coal or tapping into deposits of oil
and natural gas is only the first step in refining fossil fuels in order to
generate electricity from fossil fuels. This non-renewable source of
electricity is not environmentally friendly.
Which of the following is not an example of a renewable source of energy?
a. mining coal
b. a solar calculator
c. a windmill
d. capturing the energy of Niagra Falls
SF pp.
SIA pp.351-352
describe the by-products of electrical generation and their impacts on the
environment (e.g., identify by-products and potential impacts of coal-fired
electricity generation)
Air pollution from burning fossil fuels:
Fly ash:
When coal is burned fly ash is released into the air. Fly ash contains mercury, a
poisonous metal that can damage the nervous system.
sulfur dioxide- has been identified as causing acid rain
nitrogen oxides- major cause of air pollution and acid rain
carbon dioxide- has been identified as causing global warning
Strip-mining:
Strip-mining is used when deposits are near the surface. Coal is often mined
using this method, and the coal can be used to generate electricity. This type of
mining removes all plants and animals from the area. The natural environment
is never fully restored.
Oil and gas fired generators:
Oil or gas is burned to heat water, which becomes steam and turns a turbine to
generate electricity. This process releases poisonous gases and warm water into
nearby lakes and rivers. There is a need to monitor plants and animals in the
area to ensure their health.
Oil is pumped from wells, sometimes by injecting water into the ground. A
significant amount of fresh water goes into the ground, out of the water cycle
forever. Natural gas wells produce sour gas which is poisonous.
There are several important environmental issues about power generation in
Alberta.
i. Debris occasionally plugs the penstock of a dam
ii. Fly ash settles on the surrounding fields
iii. Thermal warming of water used in coal generators kills fish
iv. Flooding of large land masses disturbs nature
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Place the number 1 if the issue is related to fossil fuel generated power and a
number 2 if it is related to water generated power.
______ ______ ______ ______
i
ii
iii
iv
SF pp.
SIA pp.354-358
identify example uses of electrical technologies, and evaluate technologies in
terms of benefits and impacts (e.g., identify benefits and issues related to the
use of electrical technologies for storing and transmitting personal
information)
Some technologies based on electricity:
 computers- may make tasks more time efficient
- more instant communication
- lots of waste produced when computers are discarded
 lasers
- used in cd players, medical applications such as surgeries,
dental work, communication
- the cost can be downside, although the cost is decreasing
 cell phones- instant communication of words and pictures
- a person is almost always reachable
In general, many people would argue that technology had made our lives easier.
Some would argue, however, that we are experiencing an information overload
and are working harder than ever as a result of technology.
SF pp.
SIA pp.352-353
identify concerns regarding conservation of energy resources, and evaluate
means for improving the sustainability of energy use
Some concerns:
 shrinking natural resource reserves
 increasing demand on natural resources
 environmental concerns with the means in which resources are obtained,
used, and discarded
Some ways to improve the sustainability of energy use:
 manage resources according to what we have rather than what we use
 improve the efficiency of machines and appliances
 use more renewable sources of energy, and avoid the the use of nonrenewable energy sources
 make good personal choices
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