Download UNIT D: ELECTRICAL PRINCIPLES ANDTECHNOLOGIES

Science 9
Unit 4
Electrical Principles and
Technologies
Study Guide
Study Guide: This will be your primary study source for the unit.
Text: Science in Action 9 (pages given) or Science Focus 9
Unit Exam Date: TBA
Unit Overview: Electricity provides the means to energize many devices, systems and
processes that are part of our technological environment. Electrical devices are used to
transfer and transform energy, to provide mechanisms for control and to transmit
information in a variety of forms. In this unit, students learn the principles that underlie
electrical technologies, by studying the form and function of electrical devices and by
investigating ways to transfer, modify, measure, transform and control electrical energy.
Using a problem-solving approach, students create and modify circuits to meet a variety of
needs. Students also develop skills for evaluating technologies, by comparing alternative
designs and by considering their efficiencies, effectiveness and environmental impact.
Focusing Questions: How do we obtain and use electrical energy? What scientific principles
are involved? What approaches can we use in selecting, developing and using energyconsuming devices that are efficient and effective in their energy use?
Marking: (approximate)
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Unit Exam
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UNIT 4 - Electrical Principles and Technologies Curriculum Overview
A. Investigate and interpret the use of devices to convert various forms of energy to
electrical energy, and electrical energy to other forms of energy.
1. identify, describe and interpret examples of mechanical, chemical, thermal (heat) and
electrical energy
2. investigate and describe evidence of energy transfer and transformation
3. investigate and evaluate the use of different chemicals, chemical concentrations and
designs for electrical storage cells
4. construct, use and evaluate devices for transforming mechanical energy into electrical
energy and for transforming electrical energy into mechanical energy modify the design
of an electrical device, and observe and evaluate resulting changes
B. Describe technologies for transfer and control of electrical energy.
1. assess the potential danger of electrical devices, by referring to the voltage and current
rating (amperage) of the devices. Distinguish between safe and unsafe activities
2. distinguish between static and current electricity, and identify example evidence of each
identify electrical conductors and insulators, and compare the resistance of different
materials to electric flow
3. use switches and resistors to control electrical flow, and predict the effects of these and
other devices in given applications describe, using models, the nature of electrical
current; and explain the relationship among current, resistance and voltage measure
voltages and amperages in circuits, and calculate resistance using Ohm’s law
4. develop, test and troubleshoot circuit designs for a variety of specific purposes, based on
low voltage circuits
5. investigate toys, models and household appliances; and draw circuit diagrams to show the
flow of electricity through them
6. identify similarities/differences between microelectronic circuits/circuits in a house
C. Identify and estimate energy inputs and outputs for example devices and systems, and
evaluate the efficiency of energy conversions
1. identify the forms of energy inputs and outputs in a device or system
2. apply appropriate units, measures and devices in determining and describing quantities
of energy transformed by an electrical device
3. apply concepts of conservation of energy and efficiency to the analysis of devices
4. compare energy inputs and outputs of a device, and calculate its efficiency
5. investigate techniques for reducing waste of energy in common household devices
D. Describe the societal and environmental implications of the use of electrical energy
1. identify and evaluate alternative sources of electrical energy, including oil, gas, coal,
biomass, wind, waves, solar, nuclear and batteries
2. describe the by-products of electrical generation and their impacts on the environment
3. identify example uses of electrical technologies, and evaluate technologies in terms of
benefits and costs
4. identify concerns regarding conservation of energy resources, and evaluate means for
improving the sustainability of energy use
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Topic A: Investigate and interpret the use of devices to convert various
forms of energy to electrical energy, and electrical energy to
other forms of energy.
1. Identify, describe and interpret examples of mechanical, chemical, thermal (heat) and
electrical energy. (Textbook Pg. 318 – 321)
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What is energy? The ability to do work or cause change
What are the five main energy tasks?
Energy gives us light.
Energy gives us heat.
Energy makes things move.
Energy makes things grow.
Energy makes technology work.
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There are two types of energy - stored (potential) energy and working (kinetic)
energy. For example, the food you eat contains chemical energy, and your body stores
this as potential energy until you release it (kinetic energy) when you work or play.
Kinetic energy is commonly confused with mechanical energy but they are completely
different.
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Energy comes in many different forms, including solar (light), mechanical, chemical,
electrical, thermal (heat), and nuclear.
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Radiant (Solar) Energy
Energy from the Sun
Commonly called light energy
All parts of electromagnetic radiation
Useful forms are light and heat from the Sun
Converted to electrical energy using solar cells
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Mechanical Energy
Puts things in motion such as turbines from turning windmills
Moves cars
Pulls, pushes, twists, turns, and throws
Machines use mechanical energy
Our bodies use mechanical energy
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Chemical Energy
Energy stored in food, wood, coal, petroleum, and other
Energy stored in chemical bonds
Food contains chemical energy that our body needs. Our digestive
system breaks up the chemical bonds, releasing the energy.
Photosynthesis in plants – plants take in sunlight, water, nutrients and
carbon dioxide. When these bonds are broken plants produce sugars and
oxygen.
Burning wood- fire breaks up chemical bonds, releasing the chemical
energy as thermal energy.
Electrical Energy
The energy of moving electrons
Electric current from a battery
Electrical current from a wall socket
Power plants produce electrical energy
Thermal (Heat) Energy
Energy of moving or vibrating molecules
The faster the molecules move, the hotter the object and the
greater the thermal energy
The heat from a fire
Anything that gives off heat has thermal energy
Nuclear Energy
The energy locked in the nucleus of the atom
Bonds between protons
Is released when atoms combine or split
Nuclear power plants split uranium atoms (fission)
The Sun combines atoms to produce helium (fusion)
Debate over whether it is renewable or not
2. Investigate and describe evidence of energy transfer and transformation.
(Textbook Pg 323 – 331, 345-346)
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Mechanical energy transformed into electrical energy
o Generators
o While Michael Faraday was experimenting with the first motor, he discovered
electromagnetic induction – current can be generated by moving a wire through
a magnetic field (or a magnet through a coil of wire). This discovery let to
generators that produce a strong and steady supply of electricity to our world
today.
o In a hand-held generator, you spin the handle and this spins a coil of wire past
magnets. Electricity is induced into the wire and it can be used to power light
bulbs, etc.
o In large scale power generating stations, the same principle is used. Massive
coils of wire are turned inside of huge magnets. The wire coil is turned by
attaching it to the shaft of a turbine (spinning shaft with blades attached).
Turbines can be turned by steam, wind or water.
o Motors and generators are very closely related. They use the same
mechanisms but are opposite of one another in terms of energy conversion.
Large Power Plant Generator.
The electrical energy is then
transferred to homes and
businesses through a power grid
such as the one shown here.
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Small Generator
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Electrical energy to magnetic energy
 Electromagnets
 In 1820, Hans Oersted discovered current carrying wires deflect
a compass needle by producing a magnetic field. Electromagnets
are the result of this discovery. The more wire coils or the
stronger the source, the stronger the electromagnetic effect.
 Electromagnets are better than permanent magnets because they can be
controlled (shut on and off) and they can be made stronger or weaker.
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Electrical energy transformed into mechanical energy
 Motor
 In 1831, Faraday made a device that would produce motion using electric current –
the first motor.
 Motor parts:
*Source (battery)
*Terminals (where battery attaches to motor
*Brushes (carry current to commutator)
*Commutator (split ring reverses direction of
current flow to armature)
* North and south permanent magnets
attract and repel the armature
*Armature – electromagnets on each end cause
it to spin as it is alternately attracted and repelled by
permanent magnets.
 The spinning armature is attached to a shaft that can turn wheels, fans, etc.
 To make motor stronger, use stronger source, more coils on armature, stronger
permanent magnets.
 To reverse motor direction, change the connections around on the battery
terminals or change the direction of the permanent magnets. This is referred
to as changing the polarity (direction of current flow).
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Thermal energy to electric energy
o Thermocouple
When different metals are subjected to heat on one end and cold on the other,
electrons become agitated and move. These moving electrons generate a current
in a circuit that is attached to the metal. The greater the difference in
temperature, the more current a thermocouple generates. Metals must be
different or there is no potential difference (voltage) set up.
o Recovery operations use thermocouples to generate electricity from the heat
wasted during incineration of garbage. In this way, some of the wasted energy is
recovered.
o Thermocouples can also be used as thermometers. Since the greater the
temperature difference the greater the voltage, you can tell the temperature by
reading how high the voltage is.
o Thermocouples are used in furnaces to let them know when to shut on and off by
reading a current. When a certain current is attained, the furnace shuts off or
starts up. In this way, they act as a switch (also called a thermostat).
3.
Investigate and evaluate the use of different chemicals, chemical concentrations and
designs for electrical storage cells. (Textbook Pg 288-292)
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Chemical energy to electrical energy
o Cells and batteries
o An acid (electrolyte) and base react to create voltage.
o A simple flashlight converts chemical to electrical energy
and then electrical energy to light energy.
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Cells (wet or dry) have two electrodes which are metals of different reactivity (zinc and
copper, for example). The greater the difference in reactivity
between electrodes, the more voltage the cell creates.
Cells have an electrolyte which is an ion solution that can conduct
electricity. The stronger the electrolyte, the more voltage the cell
will produce. The best electrolytes are strong acids (sulfuric acid)
but saltwater also works well. The ions (positive and negative atoms)
freely move from one electrode to the other and that is how they
conduct electricity.
The electrolyte reacts with the different electrodes in different
ways so one becomes positively charged and one negatively charged.
When the (+) and (-) metals are connected to a circuit through terminals, current will flow
from the (-) to (+) electrode. Placing a load (such as a light bulb) in this circuit will allow the
electrical energy to be converted to some other useful form of energy.
Basic cells like the ones you buy in the store are 1.5 V. More than one cell can be combined
to form a battery. Ex. Two 1.5 V cells make a 3V battery.
Wet cells and dry cells are similar but the electrolyte is liquid in a wet cell and paste in a
dry cell. Dry cells are used more for portable, continuous, longer lasting energy while wet
cells are more for a powerful initial electrical boost such as the one used to start an
automobile.
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Direction of current flow
Wire
WET CELL
V
Negative terminal
Liquid
Electrolyte
DRY CELL
Positive terminal
Zn
Cu
Electrodes
Positive terminal
(copper)
Electrolyte
Paste
wire
V
Negative terminal
(zinc)
Direction of current flow
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Solar cells or photovoltaic cells (PV cell) offer a limitless and environmentally
friendly source of electricity. The solar cell is able to create electricity directly
from photons. When photons hit the solar cell, freed electrons (-) move toward
one direction leaving a positive charge in the opposite direction. If a circuit is
attached, the electrons flow from the negative pole to the positive pole as
electrical current. Solar cells may be very large to provide electricity to buildings
or they may be very small such as the ones in calculators.
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Topic B: Describe technologies for transfer and control of electrical energy.
1. Assess the potential danger of electrical devices by referring to the voltage and current
rating (amperage) of the devices. Know what activities are safe and unsafe. (Textbook Pg
284-287)
 A short circuit occurs whenever electricity bypasses the normal pathway in a circuit. When
you become that pathway, you are electrocuted.
 Consider voltage and amperage when talking about electrical danger. Amperage is the current
that actually flows through your body so high amperage is very dangerous. Voltage is the
“pressure” that it is pushed with so although it is dangerous, it doesn’t do the damage that
current does. 0.01 A can make your arm go numb and 0.1 A can be fatal. You should be aware
of an appliances amperage. For example, computers draw about 0.8 amps while microwave
ovens draw 9.0 amps. Therefore, microwaves are a greater electrical hazard than computers
even though both are powered by 120 V house wiring. 15 V can give you a nasty shock and 120
V (household voltage) could kill if you are wet. However, it usually takes higher voltage to kill.
 A few hints – jump from a car with a downed power line, don’t step out.
Don’t be the tallest thing around or under the tallest thing around during a lightening storm.
Ground wires (wires leading electricity into the ground and away from where it could do harm)
should never be removed.
Don’t bypass safety fuses. If the circuit is supposed to have a 1 A fuse, don’t put a 2 A fuse
in instead. The circuit will get too hot and could start a fire. Fuses limit the amount of
current that can move through a circuit. If current gets too high, the fuse gets so hot
that it melts through, breaking the circuit.
Know how to operate circuit breakers (gray boxes with switches that flip off when a circuit
overheats). They are designed to make sure that circuits are not overloaded to the point
where they start a fire. For example, let’s say you have a 15 amp circuit breaker. You
could add a 7 amp heater and a 3 amp drill. However, if you tried to plug in a 6 amp fan,
that would be more than 15 amps so the circuit breaker would flip and your power would
be shut off. You would have to unplug one of the devices before it would work.
Avoid frayed wire. Don’t overload a circuit. Unplug appliances before fixing them.
Circuit Breaker Box
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Fuse
2. Distinguish between static and current electricity, and identify example evidence of
each. (Textbook Pg 275-280)
 Benjamin Franklin experimented with his key and kite to try
and discover the electrical properties of lightning. What he
captured was static electricity.
 Static electricity is a stationary change that builds to a point
where it suddenly discharges. Positively charged particles
+
+
+
(missing an electron) attracts negative charged particles (one
too many electrons). Lightning is an example, as is static cling.
Materials with atoms that are oppositely charged will attract one another while materials with
atoms that are the same charge will repel one another. Any charge atom is attracted to an
opposite or a neutral charge.
 Current electricity is a steady flow of charged particles through a
conductor. It flows until its source is cut off. All of our electrical
devices use current electricity, for example, flashlights, and motors.
Most of our electricity comes from cells or from electrical
generators.
3. Identify electrical conductors and insulators, and compare the resistance of different
materials to electric flow. (Textbook Pg 297-301)
Conductor
Examples
Metals (copper)
Insulators
Rubber, glass, air
Semiconductor
Superconductor
Resistors
Carbon, silicon
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Extremely cold
metals
Nichrome and
Tungsten wire
Characteristics
Material that conducts electrical
energy (allows current to flow)
Material that does not allow the flow
of electricity through it.
Properties of both conductors and
insulators.
Almost perfect conductor (almost no
resistance to flow)
Conductor that resists the flow of
electricity. It retains the energy
rather than letting it pass.
Uses
Used in circuits
to conduct electricity
Protection from
electrical shock
Microchips,
Rheostats
M.R. I.s
Light bulbs, heaters,
dimmer switches
Lie detectors work on the principle of resistance and conductivity. When people lie they
sweat. Sweat is saltwater which is a good conductor so the machine registers decreased
resistance (increased conductivity) when someone is lying.
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How Light Bulbs Work – The electrical
current enters the bulb through the hot
wire and continues along the circuit to the
tungsten filament. Tungsten is more
resistant than copper wire so the
electricity must work harder to get
through. Also, the tungsten is stretched
very thin and wound into a tight coil. The
small diameter and increased length
increases the resistance even more. This
means that the tungsten wire gets so hot,
that it starts to glow. If it gets too hot, it
will break and you will need to replace your
bulb.
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How does a toaster work – There are coils inside a toaster of high resistance wire.
When the toaster is turned on, the coils heat up because of their increased length due
to coiling and their high resistance. The heat is used to toast bread.
4 . Investigate electrical devices and draw circuit diagrams to show the flow of electricity.
(Textbook Pg 311-312)
Component
Circuit Symbol
Lamp (lighting)
or
Motor
or
Fuse
Fuse
~
Cell
Battery
Battery
Photocell
Wire
Voltmeter
Ammeter
Galvanometer
Ohmmeter
LED
Light Emitting Diode
Resistor
Resistor
Variable Resistor
Rheostat
On-Off Switch
2-way Switch
Circuit diagrams are designed to give everyone
who deals with electrical components a common
and simple language.
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Function of Component
This symbol is used for a lamp providing
illumination, for example a light bulb.
A device which converts electrical energy to
kinetic energy (motion).
A safety device which will 'blow' (melt) if the
current flowing through it is too high.
Another symbol sometimes use for a fuse
Supplies electrical energy. Single cell (1.5 V)
Supplies electrical energy. A battery is more
than one cell. This one represents an
unknown number of cells.
Another symbol for a battery that defines
number of cells. This is a 4.5 V battery.
A photocell. Light will either turn a circuit
with this cell on or off.
To pass current very easily from one part of
a circuit to another.
A voltmeter is used to measure voltage.
An ammeter is used to measure current.
A galvanometer is a very sensitive meter
which is used to measure tiny currents.
An ohmmeter is used to measure resistance.
Most multi-meters have an ohmmeter setting.
A transducer which converts electrical
energy to light.
A resistor restricts the flow of current.
Another common symbol used for resistors
Used to adjusting lamp brightness, adjusting
motor speed, and adjusting the rate of flow.
Symbol used specifically for rheostat
An on-off switch allows current to flow only
when it is in the closed (on) position.
A 2-way switch directs the flow of current
to one of two routes according to its position.
5. Use switches and resistors to control electrical flow, and predict the effects of these
and other devices in given applications. (Textbook Pg 302)
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Switch on – metal contacts wire so circuit is complete and electricity flows.
Switch off – metal does not contact wire so circuit is incomplete - electricity does not
flow.
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Simple circuit switch
 When this switch is closed the light goes
on. When it is open as it is in this picture,
the light stays
off. This switch
is in the closed
position.
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Rheostat is a variable resistor switch
 usually uses resistive wire such as nichrome or
semiconductor such as carbon. If current flows
through more of the resistor, the light dims
because energy is going to the resistor (it heats
up). If it goes through less resistor, the light
brightens so you can control brightness. Rheostats
can be used to control brightness, volume, speed
(motor) and temperature (heater).
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Doorbell switch
This diagram shows an interesting variation of wiring.
The 2 doorbell buttons do not have to be right next to
each other. One button could be at a front door and
the other at a side door. If you follow the circuit, you
can see that pressing either button will cause the
doorbell to ring. The 2 switches are said to be wired in
parallel.
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Push doorbell in
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3-Way Switch
 This allows you to turn lights on and off at different locations, for example the
top and bottom of stairs.
On
Off
Switch
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A photocell is a device that acts like a switch when it is activated by
electromagnetic energy in the form of light waves. Photoelectric cells exist in
many types, and are used for many things. It is a
type of electric cell whose operation depends upon
the extent to which it is exposed to light. The most
familiar one is when a door seems to open by itself
when we approach it. This happens because our body
blocks a beam of light and a photoelectric cell makes
the door open. It is also commonly used for security
alarms. The photoelectric cell is often referred to as
an “electric eye”.
6. Describe, using models, the nature of electrical current and explain the
relationship among current, resistance and voltage. (Textbook Pg 304-306)
Using the flow of water as an analogy can make concepts of electricity easier to
understand. The flow of electrons in a circuit is similar to water running through a
hose. If you could look into a hose at a given point, you would see that a certain
amount of water passes that point each second. The amount of water depends on how
much pressure is being applied––how hard the water is being pushed. It also depends
on the diameter of the hose. The more forceful the pressure and the larger the
diameter of the hose, the more water passes each second. The flow of electrons
through a wire depends on the electrical pressure pushing the electrons and on the
cross-sectional area of the wire.
Voltage
The pressure that pushes electrons in an electrical circuit is called voltage.
Using the water analogy, if a tank of water were suspended
one meter above the ground with a one-centimeter pipe
coming out of the bottom, the water pressure would be
similar to the force of a shower. If the same water tank
were suspended 10 meters above the ground, the force of
the water would be much greater, possibly enough to hurt
you. (If you jumped from a one-meter diving board, the
force when you hit the water would not be too great. If
you jumped from a 10-meter board, the force would be
much greater.) Voltage (V) is a measure of pressure, or
electromotive force, applied to electrons to make them
move.
It is a measure of the strength of the electric current in a
circuit. Voltage is measured in volts (V). A volt is the
amount of electromotive force (emf) needed to push a
current of one ampere through a resistance of one ohm. This definition will make
more sense after you learn about current and resistance. Just as the 10-meter tank
applies greater pressure than the 1-meter tank, a 10-volt power supply (such as a
battery) would apply greater electromotive force than a 1-volt power supply. Voltage
potential is the electrical term that is analogous to water pressure. AA batteries are
1.5-volt; they apply a small amount of voltage or pressure for lighting small flashlight
bulbs. A car usually has a 12-volt battery––it applies more voltage to push current
through circuits to operate the radio or defroster. The standard voltage of wall
outlets is 120 volts––a potentially dangerous amount of voltage. An electric clothes
dryer is usually wired at 240 volts––a very dangerous amount of voltage.
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Current
The flow of electrons can be compared to the flow of
molecules of water. The water current is the number of
molecules flowing past a fixed point; electrical current is
the number of electrons flowing past a fixed point.
Electrical current is defined as electrons flowing
between two points having a difference in voltage
potential. Current is measured in amperes or amps (A).
One ampere is 6.25 x 1018 electrons per second passing
through a circuit. With water, as the diameter of the
pipe increases, so does the amount of water that can flow
through it. With electricity, a conducting wire is the pipe.
As the cross-sectional area of the wire increases, so does the amount of electric
current (number of electrons) that can flow through it.
Resistance
Resistance is a property that slows the flow of
electrons––the current. Using the water analogy,
resistance is an impediment to water flow. It could be a
smaller pipe or fins on the inside of a pipe. In electrical
terms, the resistance of a conducting wire is dependent
on the metal used to make the wire, and the diameter of
the wire. Copper, aluminum, and silver––common metals
used in conducting wires––all have different resistance
properties. Resistance is a characteristic property of a
conducting material. Resistance is measured in units
called ohms Ω). There are electrical devices, called
resistors, designed with specific resistance that can be
placed in circuits to reduce or control the flow of the
current. Every electrical appliance contributes
resistance to a circuit, as well. Any appliance or device
placed within a circuit to do work is called a load. The light bulb in a flashlight is a
load. A television plugged into a wall outlet is a load. Every load introduces
resistance in a circuit.
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Ohm’s Law
George Ohm, a German physicist, made an important discovery about electricity in
the early 19th century. He found that in many materials, especially metals, the
current that flows through a material is proportional to the voltage across the
material. In the substances he tested, he found that if he doubled the voltage (V),
the current (A) also doubled. If he reduced the voltage by half, the current dropped
by half. The resistance (Ω) of the material remained the same whether the voltage
and current increased or decreased. This relationship is called Ohm’s Law, and can be
written in three simple formulas. If you know any two of the measurements, you can
calculate the third using these
formulas:
7. Measure voltages and amperages in circuits, and calculate resistance using Ohm’ Law.
(Textbook Pg 306-308)
Current (I) is
measured in
Amps (A)
Voltage is
measured in
Volts (V)
Resistance is
measured in
Ohms (Ω)
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Measures amount of electrical current. Measure using an ammeter (measures
Most household devices have low
exact current) or a galvanometer
amperage (i.e. a kettle uses 13 A).
(measures very low currents).
Galvanometers can be made from
a wire and compass.
Measure of how much
Measure using a voltmeter. Measure
Electrical energy each charged
the potential difference in amount of
Particle has. The higher the
electrical energy from one point to
Voltage, the greater the
another. Digital or analogue (read scale
Potential Difference.
very carefully!).
Household voltage 120 V,
Cells 1.5 V.
Measures how difficult it is for
Measure using an ohmmeter.
electricity to flow. Nichrome wire
To calculate, R = V/I. For example, if
has very high resistance so it is
you have a 3 Volt battery and a 6 amp
difficult for current to pass. Copper
bulb in a circuit, resistance would be
wire has very low resistance so
R = 3/6 = 0.5 ohms. The greater the
current flows easily.
resistance, the more heat you have.
Multimeters can be used to measure all three properties with one instrument.
Ammeter for current
Hand made galvanometer to measure
small amounts of current
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Voltmeter for voltage
Multi-meter measures
current, voltage and resistance
Parallel and Series Circuits
(Textbook Pg. 311 – 315)
There are two ways of connecting components:
In series so that each component has the same current. The battery voltage is divided
between the two lamps. Each lamp will have half the battery voltage if the lamps are identical.
In parallel so that each component has the same voltage. Both lamps have the full
battery voltage across them. The battery current is divided between the two lamps.
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Series
Parallel
The terms series circuit and parallel circuit are sometimes used, but only the simplest
of circuits are entirely one type or the other. It is better to refer to specific
components and say they are connected in series or connected in parallel.
If several lamps are connected in series they will all be switched on and off together
by a switch connected anywhere in the circuit. The
supply voltage is divided equally between the lamps
(assuming they are all identical). If one lamp blows, all
the lamps will go out because the circuit is broken.
G
If several lamps are connected in parallel each one has the
full supply voltage across it. The lamps may be switched on
and off independently by connecting a switch in series with
each lamp as shown in the circuit diagram. This
arrangement is used to control the lamps in buildings.
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G
SERIES
Example
Description
Flashlight
Current
passes
through
each load in
turn so
voltage is
shared
Separate
current for
each path
so each
load gets a
full share
of voltage
Switches in
homes
PARALLEL
Household
wiring
Most tree
lights
Adding
loads
Each added
load means
less
voltage for
others so
lights dim
Removing
loads
When one
load burns
out, others
all go out
since circuit
is broken
No
difference
since all
loads get
full amount
of voltage
Other loads
stay on since
they have a
separate
conductor
back to
source
Adding cells
Advantages
Disadvantages
Cells added in
series result
in added
voltage (i.e.
two 1.5 V
cells add up
to 3V battery
Cells added in
parallel do
not increase
voltage but
they do make
each cell last
longer
Simple to
construct
Circuit all
goes off if
one load burns
out
Uses less
energy
Flexibility in
operating
loads
together or
separately
More complex
to construct
Use more
energy
Circuit Diagram
Symbols for Cells:
Cells in Series
Series
Parallel
Cells in Parallel
8. Identify similarities and differences between microelectronic circuits and circuits in a
house. (Textbook Pg 315)


Resistors of various values (i.e. 0.1Ω to 200Ω ) are used in electronics. They are
used to control how much current is allowed to flow to each component in a complex
circuit. Microcircuits have very low resistance and amperage compared to regular
circuits.
Transistors are used as switches in tiny microcircuits. They can stop or start current
in several different directions at once. They basically do the same thing as switches
in larger circuits.
Transistor
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Resistor
Motherboard
Topic C: Identify and estimate energy inputs and outputs for example devices
and systems, and evaluate the efficiency of energy conversions.
1. Identify the forms of energy inputs and outputs in a device or system. (Textbook Pg 321)





Electrical – potential energy of charged particles released when they flow or
discharge (i.e. generator).
Mechanical - energy of moving objects or potential energy of objects that could move
(i.e. rock on edge of cliff).
Thermal – energy of vibrating particles in a substance. The faster the particles move,
the more heat energy produced (i.e. hot water).
Chemical – potential energy stored in chemicals and released when there is a chemical
reaction (i.e. battery).
Some common energy conversions include:
Input energy
Mechanical
Output energy
Electrical
Device
Generator
Chemical
Electrical
Cell or battery
Electrical
Chemical
Thermal
Electrical
Chemical
Light
Mechanical
Electrical to thermal
Electrical
Thermal
Mechanical
Electrical
Motor
Light bulb
Thermocouple*
Oven
Digestion
Photocell
Input energy is what you start with, while output energy is the end result.
A transformer is an electrical device that takes electricity of one voltage (usually
very high voltage power lines) and changes it into another voltage (usually lower
voltage house current). You'll see transformers at the top of utility poles, in the
green boxes in neighbourhoods and even changing the voltage in a toy train set.
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2. Apply appropriate units, measures and devices in determining and describing quantities of
energy transformed by an electrical device. (Textbook Pg 332-333)
Electrical Power
Power is a measure of the rate of doing work or the
rate at which energy is converted. Electrical power is
the rate at which electricity is produced or consumed.
Using the water analogy, electric power is the
combination of the water pressure (voltage) and the
rate of flow (current) that results in the ability to do
work. A large pipe carries more water (current) than a
small pipe. Water at a height of 10 meters has much
greater force (voltage potential) than water at a
height of one meter. The power of water flowing
through a 1-centimeter pipe from a height of one
meter is much less than water through a 10centimeter pipe from a height of 10 meters.
Electrical power is defined as the amount of electric
current flowing due to an applied voltage. It is the
amount of electricity required to start a device or operate a load for one second.
Electrical power is measured in watts (W). The formula for power that quantifies this
relationship is:
Measuring electrical power can be confusing because a watt does not sound like a
rate. Usually we think of rates as ratios––miles per hour or miles per gallon. A watt is,
in fact, a ratio; you must learn about another measurement to understand it––a joule.
A joule is a measurement of work performed. One watt is the rate of doing work
when one joule of energy is used in one second (1 watt = 1 joule/second).
A 50–watt light bulb uses electrical power at a rate of 50 joules per second. A 100--watt light bulb uses electrical power at the rate of 100 joules per second.
For example, you are using a drill that draws 12 amps from a 6 volt battery.
How much power is consumed by this drill?
P=IxV
= 12 x 6
= 72 watts
A kilowatt hour is a measure of power. It is just a larger unit for measuring large
amount of electrical power use such as at your house.
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Energy
 E=Pxt
Energy is the ability to do work.
Energy = Power x Time
For example, you turn on a 100 watt bulb in your bedroom and leave it on for one hour.
How much energy did you consume?
E=Pxt
= 100 x 3600 (remember to convert 1 hour to seconds by multiplying by 3600)
= 360 000 joules (or 360 kJ or 0.36 MJ) MJ = megajoule kJ = kilojoule
When you are dealing with watts or joules, the unit of time is always seconds. You
often need to convert minutes (x60) or hours (x 3600) to seconds when doing
problems.
3. Apply the concepts of conservation of energy and efficiency to the analysis of energy
devices (light bulbs). (Textbook Pg 338)

Some devices are more efficient than others. Incandescent bulbs are only 5%
efficient, meaning 5 joules of light are produced. The rest of the energy doesn’t just
disappear. It can’t, according to the law of conservation of energy. The other 95
joules is converted to unwanted heat. Fluorescent bulbs are 20% efficient.
4. Compare energy inputs and outputs of a device and calculate its efficiency. (Textbook Pg
335-336)

Ef = Eo / Ei x 100
Efficiency = Energy output / Energy Input
% = joules/joules
For example, you are using a gasoline powered trimmer on the grass. You will need to
add 2100 joules of energy from the gasoline in order to get 700 joules of useful work
from the trimmer. What is the efficiency of the gas trimmer?
Ef = Eo / Ei x 100
Ef = 700 / 2100 x 100
Ef = 33.3 x 100
Ef = 33%
The smaller the number, the less efficient the device will be. No machine is 100%
efficient. There is always some energy wasted through heat loss, sound, motion, etc.
For example, if a hair dryer used 140 J of electrical energy and was able to produce
20 J of usable energy in the form of mechanical (fan) and heat, the efficiency of the
hair dryer would be [(20 ÷ 140) x 100 = 14% efficiency].
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5. Investigate and describe techniques for reducing waste of energy in common household
devices. (Textbook Pg 339-342)
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
There are lots of things that people can do to reduce energy waste. For example:
o Make sure that moving mechanisms are well-lubricated to reduce friction.
o Use more efficient types of light bulbs (energy efficient fluorescent or
halogen bulbs)
o Don’t over dry clothes
o Don’t use an entire wash cycle for a pair of socks
o Turn off the lights!

Energuide labels help us increase efficiency by showing us
which devices are the most efficient before purchasing them.
The label tells the average number of kWh it would use in a
year and compare its efficiency on a scale with other models.
Most efficient appliances have insulation that keeps warmth
or cold in so that electricity is conserved.

Reducing friction, using more insulation, etc. are ways of
making energy more efficient. You can reduce friction by using ball bearings,
lubricants or fewer moving parts.
Topic D: Describe and discuss the societal and environmental implications of
the use of electrical energy.
1. Identify and evaluate alternative sources of electrical energy, including oil, gas, coal,
biomass, wind, waves, solar and batteries. (Textbook Pg 345-350)
Source
Fossil fuels (coal, oil, natural
gas). Most of Alberta’s energy
is from burning coal. The fire
heats steam that then turns a
generator turbine.
Wind. The wind turns blades on
a windmill that are attached to
a turbine on an electrical
generator.
Waves/Tides. Turbines
attached to generators are
placed offshore and turn when
tides come in and out twice a
day.
Biomass. Trees, agricultural
waste, manure, sewage, scrap
wood from construction, etc.
This is burned and the fire
heads steam that then turns a
generator turbine.
Battery-powered cars. These
would be lead-acid batteries.
Advantages
Relatively cheap,
technology is already in
place.
Disadvantages
Non-renewable, pollution from
burning fossil fuels is dangerous for
the environment.
Renewable ,clean
Location - limited
Renewable, clean
Location - limited
Renewable resource.
The burning does produce some
sulfur dioxide and nitrogen oxide
(acid rain) but far less than fossil
fuels.
Wouldn’t have the
pollution from burning
fossil fuel.
Nonrenewable. Cars will be heavier,
slower and won’t go as far as
regular cars because of the weight
of the battery. The lead-acid
batteries will release toxic lead into
the environment and making the
batteries would create industrial
waste.
Hydrogen can be dangerous if not
handled properly. Auto
manufactures are still perfecting
the design but the first cars should
be out very soon.
(This idea has pretty much been
abandoned by car
manufacturers)
Fuel Cell powered cars. Cars
would carry compressed
hydrogen gas that would mix
with oxygen in a chemical
reaction that produces water.
Energy released turns a motor
which turns axles on car.
Solar. Solar panels convert
thermal energy to electrical
energy.
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Renewable. Twice as
efficient as fossil fuels.
Quiet – no internal
combustion engine. The
only waste product is
water.
Renewable, clean.
Location is limited. Expensive.
Takes up lots of space.
2. Describe the by-products of electrical generation and their impacts on the
environment. (Textbook Pg 351-353)
 Most electricity in Alberta is generated from burning coal. Byproducts include:
o Sulfur dioxide – combines with water in the air to produce sulfuric acid,
causing acid rain.
o Nitrogen oxide – combines with water in the air to produce nitric acid, causing
acid rain.
o Carbon dioxide – a byproduct of any burning, CO2 is a greenhouse gas and is
causing our Earth to warm excessively.
o Fly ash (very fine particulate) contains mercury and arsenic. These toxins
then settle into water systems where they become more concentrated.
3. Identify example uses of electrical technologies and evaluate technologies in terms of
benefits and impacts. (Textbook Pg 354-358)
 Used for heat, light, movement, communication
 Binary system – electrical systems communicate using two numbers – 0 and 1.
Basically, 0 is off and 1 is on. The microcircuits in the electrical system are told to
turn on and off in order to create a code that can be translated into usable
information.
 One of the most recent technologies has been in the field of communication.
Computers, and especially the internet have allowed us to become a single, global
community.
 Benefits – better understanding of the world, ability to do business without having to
travel great distances, saves time, opens up a world of information that was not
available before
 Drawbacks – your personal information, including financial information, is easily
available to those who know how to get it, you are never really sure who you are
“talking” to, you don’t know if the information you read is accurate or not, your
personal computer can be attacked by viruses that wipe out important information
that you have saved, prosperous countries are at an advantage
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4. Identify concerns regarding conservation of energy resources, and evaluate means for
improving the sustainability of energy use. (Textbook Pg 350)
 Most of our energy is produced through non-renewable resources (fossil fuels). Once
these are used up, we will no longer be able to produce energy the way that we now do.
 Finding alternative energy sources can be very expensive and if you live in the wrong
place, it can be almost impassible. Also, it will take a tremendous amount of time to
convert our society from fossil fuel consumption to other forms of energy.
 In order to make our energy last as long as possible, it will be important to conserve
by not wasting as much as we do. We can also find sustainable ways to use our
resources. This means that we use some, but we have a plan in mind that will make
sure the resources will also be available for future generations. For example,
selective logging uses the old trees but does not cut down the young ones. In that
way, they will be ready in years to come. Some coal burning operations are mixing
biomass in so that the coal will be there in the future if we still haven’t converted to
another source.
SKILLS TO KNOW
1. Ask questions about the relationships between and among observable variables, and plan
investigations to address those questions.
 Rephrase questions in a testable form. For example, instead of “Why do we use
parallel circuits rather than series circuits in household wiring?” a testable questions
would be “How do series circuits and parallel circuits respond differently under load?”
 Predict the amount of current in a circuit of known resistance and applied voltage (as
voltage increases, so will current).
 Provide operational definitions (concrete, measurable) for current, resistance, voltage
and polarity (direction of current flow).
2. Conduct investigations into the relationships between and among observations, and
gather and record qualitative and quantitative data.
 Estimate the efficiency of a mechanical device based on how much heat it produces.
 Use ammeters and voltmeters to make accurate measurements.
3. Analyze qualitative and quantitative data, and develop and assess possible explanations.
 Evaluate the safety, durability, efficiency and environmental impact of a personallyconstructed wet cell design.
 Measure the current in similar circuits, and provide possible explanations for
differences in current flow (series versus parallel).
4. Work collaboratively on problems and use appropriate language and formats to
communicate ideas, procedures and results.
 Use charts to present data on the voltage, current (amperage) and resistance found in
series and parallel circuits).
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