Download EPT Student Notes - Holy Cross Collegiate

Science 9
Electric Principles and Technology
Mrs. Sample
Christ the Redeemer Catholic Schools
Science 9
Topic 1: Electrical Charges
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Materials that attract and repel other materials are said to be charged, or carry an electrical
charge.
Electric charge can be detected by an instrument called an __________________________.
Pocket-sized electroscopes called _______________________ are used to measure exposure
to atomic radiation.
In many cases, charges produced by rubbing or touching materials remain stationary, so they
are sometimes called static electricity. There are many instances when these charges move,
so unbalanced charges is a more accurate way of describing the phenomenon.
The quantity of electric charge is expressed in coulombs (C).
A bright light bulb allows about 1 coulomb of electric charge to pass through it every second.
Making Sense of Electric Charges
 The charge on an object depends on the balance between positive and negative charges in the
object.
a) neutral (“ uncharged”) have _________________________________________________
b) positive charge has ________________________________________________________
c) negative charge has _______________________________________________________
 Benjamin Franklin was the first to use the terms “positive” and “negative” to describe
charges.
 The charge on amber that had been rubbed with fur was called ________________________.
 The charge left on the fur was called _________________________.
Figure 1: The Laws of Charges
 Unbalanced charges on solid materials are due to
___________________________________ from one object to
another.
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The Laws of Charge:
1. Unlike charges attract.
2. Like charges repel.
3. Charged objects attract uncharged (neutral) objects.
Conductors, Insulators, and In-between
 _________________________ are materials that do not allow
charges to move freely on or through them.
 Materials that allow charges to move freely are classified as _______________________.
 Most metals are conductors and most non-metals are insulators
 A conductor holds its electrons ___________________.
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Insulators hold their electrons ____________________________.
Semiconductors are materials with ______________________________________________
__________________________________________________________________________.
The conductivity of semi-conductors is often increased by implanting foreign atoms into the
otherwise pure material.
Two commonly used semiconductors are _____________ with ______________ added, and
______________________ with _____________________ added.
Superconductors are materials that offer little, if any, resistance to the flow of charges.
Certain materials become superconductors when they are subjected to extremely low
temperatures. Superconductors _________________________________________________
_________________________________ than ordinary conductors.
Neutralizing Unbalanced Charges
 An electric discharge occurs when accumulated charge is neutralized (becomes balanced)
 In a discharge, electrons either _________________________________________________,
or ________________________________________________________________________.
 Connecting an object to Earth with a conducting wire –____________________________- is
an easy way to neutralize conducting materials
 Non-conductors, or insulators, usually must be neutralized with ionization. Ionization
devices produce both positive and negative ions. These ions are attracted to materials with an
opposite charge, transferring charges until the material is neutralized.
Preventing Electrostatic Buildup
 To decrease static buildup, antistatic sprays and coatings can be applied to carpets and other
surfaces on which charge accumulates.
 After materials have become charged, sprays can also be used to dissipate (scatter) the
charge.
 Materials that are especially sensitive to electrostatic discharge may be enclosed in special
antistatic packaging.
 Grounding straps containing conductive materials may neutralize without harmful electric
discharge.
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Topic 2: Electricity Within a Circuit
 Electric circuits provide a continuous pathway.
Circuit Elements and Diagrams
 Most complex circuits are made up of only four basic
elements.
 ________________: The source of electric energy.
 ____________________: The wire through which
current flows.
 ____________: Items along the circuit that convert
electricity into other forms of energy.
 _____________: A switch or device that can turn
the circuit or devices along it on or off.
 A battery is a combination of cells.
 You can use a switch to “open” or “close” a circuit to
control the flow of current through it.
 A resistor is used to represent one of many different
loads.
Figure 2: Basic Circuit Symbols
Measuring Current
 Electric current is ___________________________________________________________
___________________________________________________________________________
 The symbol for the current is I.
 Electric current is measured in amperes (A) or milliamperes (mA).
 An instrument used to measure very weak electric current is called a galvanometer. Larger
currents are measured with an ammeter of milliammeter. The symbols for these instruments
are a circle with “G,” “A,” or “mA” in the center, respectively.
Measuring Voltage
 The energy for pushing electrons through comes from separated positive and negative
charges.
 In a battery, _____________________________________________________ does the work
of separating the charges.
 All forms of energy are measured in joules (J).
 The energy of electrons in an electric circuit is described by a standard unit of charge instead
of the total energy of all of the changes.
 Potential difference means the difference in energy per unit of charge between one point in
the circuit and another point in the circuit. Potential difference is commonly referred to as
voltage. The standard unit for potential difference is the volt (V), named after Alessandro
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Volta (1745-1827), who built the first battery. Voltage is measured with a voltmeter; the
symbol for a voltmeter is a circle with “V” at the centre.
Current and Voltage
 Electric current is equal throughout a circuit.
 For the electric current to flow in a circuit, the battery must be supplying energy & there
must be a continuous pathway for the electric current to travel.
 Factors that affect the strength of an electric current in a circuit include
 _____________________________________________________________________
 _____________________________________________________________________
 _____________________________________________________________________
 _____________________________________________________________________
 Batteries provide electrical energy.
 Loads use electrical energy.
 The energy provided to a circuit is very close to the energy used.
 The voltage across individual loads adds up to a voltage very similar to the voltage across the
entire load.
 Voltage is higher when loads are removed because there is less resistance within the circuit.
Rivers of Electricity
 The load of an electrical circuit is comparable to a water wheel in a water system:
 A switch is comparable to a valve
 An electrical current is comparable to a flow rate
 Voltage is comparable to pressure
 A battery is comparable to a pump
 A conductor (wire) is comparable to a pipe
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Topic 3: Resisting Movement of Charge
 Resistance is a property of a substance that _______________________________________
____________________________ and converts electric energy into other forms of energy.
 If current is described as the movement of electrons through conductors, and voltage is what
makes the electrons move, then resistance is what opposes the motion of the electrons.
 A good conductor has low resistance.
 Poor conductors have high resistance.
Resistance Roadblock
 Nichrome wire is a resistor.
 The standard unit for resistance is the ohm(
)
 Resistance can be measured with an ohmmeter
 Technicians are more likely to use a multi-purpose electronic
measuring instrument (a “multimeter”) set to measure resistance
 Ohm’s law: R=V/I
ie. Resistance = Voltage (potential difference)/ Current
 Other forms of the equation are: V = IR and I = V/R
Example: What is the resistance of an electric heater, if a current of 12.5 A runs through it when
it is connected to a 120 V wall outlet? (9.60 Ω)
Example: What is the resistance of a light bulb if a 12 V battery sends a current of 2.4 A through
it? (5.0 Ω)
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Example: A toaster with a resistance of 145 Ω is connected to a 120 V source. What current will
flow through the toaster? (0.828 A)
Example: What is the potential difference across a 1500 Ω resistor carrying a current of 0.075 A
(75 mA)? (112.5 V)
Example: An extension cord rated at 15 A is connected to a 120 V supply. What is the smallest
resistance with which the cord can safely be used? (8 Ω)
Resistors
 In electronic circuits, resistance is useful for:
1) Changing the energy of moving charges into heat.
2) To control current or voltage to suit the specific needs of other electric devices in the
circuit. Circuit resistors are usually made of a heat-conducting ceramic core coated
with materials such as carbon, metal oxides, meal film, or resistance wire
Variable Resistors
 Variable resistors change in response to __________________________________________
__________________________________________________________________________.
 Varying the length of a Nichrome wire can act as a variable resistor. The longer the length,
the more resistance there is.
 Variable resistors are used in light dimmers, motor speed controls, surge protectors, and
refrigerator and stove temperature controls.
 Variable resistors are also called rheostats.
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Types of Circuits
1) _________________________ have only one current path.
2) _________________________ have several current paths.
Series and Parallel Circuits
Series Circuits
 As more bulbs are added in a series circuit,
______________________________________
because there are more resistors for the current
to travel through-more bulbs mean less current.
 In a series circuit all loads must be functional
& all switches closed for any of the loads to
work
 Advantages of series circuits:
1) ______________________________________________________
2) Less wire
3) ______________________________________________________
 Disadvantages of series circuits:
1) Additional bulbs mean dimmer lights
2) ____________________________________________________________________
Parallel Circuits
 Adding more bulbs to a parallel circuit does
not decrease the brightness of the bulbs. More
bulbs increases the current.
 In a parallel circuit not all loads need to be
functional for the circuit to work because
there are a number of paths the current can
travel
 Advantages of a parallel circuit
1) _____________________________________________________________________
2) Other loads continue to work even though one may not be working.
 Disadvantages of a parallel circuit
1) _____________________________________________________________________
2) Wires heat up with increased current flow
3) ____________________________________________________________________
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House Wiring
 Practical electric circuits for the home are _____________________________. The voltage
across each load in a parallel circuit is the same. Turning on one appliance will not reduce the
energy available to other loads.
 One potential problem does exist with parallel circuits. Current through wires connected to
the source increases whenever another branch in the circuit is closed. When you turn on any
appliance in your home, the current in the wires closest to the source increases. More current
means the temperature of the conducting wire rises.
 The wires _______________________________________________________________. To
guard against an electrical fire, household circuits always include ______________________
__________________________________.
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Topic 4 - The Energy Connection
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The scientific definition of energy is ____________________________________________.
The four most common forms of energy are:
o _________________________: potential or stored energy stored in chemicals,
released when the chemicals react
o _________________________:energy of charged particles, transferred when they
travel from place to place
o _________________________: energy possessed by an object because of its motion
or its potential to move
o _________________________: kinetic energy of a substance
Electricity and Heat
 Thermal energy can be converted directly to electric energy using a
thermocouple. A thermocouple is a loop of two wires made of
different types of metals. The wires are wrapped together at both
ends, or “junctions.” When one junction is heated, ______________
______________________________________________________
 Copper and constantan (a copper nickel alloy), or iron and
constantan, are the most common metals used in modern industrial
thermocouples.
 A thermo-electric generator is a device based on a thermocouple that converts heat directly
into electricity without moving parts. Heat from a gas burner or another heat source moves
though several thermocouples connected in series – a thermopile – creating a potential
difference. Thermopiles are extremely reliable, low-maintenance devices. They are used in
remote locations to generate limited quantities of electrical energy that are sufficient to
power, for example, emergency communications equipment.
Electricity to Motion
 Sound can be produced when __________________________________________________
_____________________________________________________ – the piezoelectric effect.
 Piezo in Greek means pressure or push. When a piezoelectric crystal such as quartz or
Rochelle salt is connected to a potential difference, the crystal expands or contracts slightly.
Material touching the crystal experiences pressure, creating sound waves or vibrations.
Motion to Electricity
 A barbecue “spark” lighter uses the piezoelectric effect in reverse. While a piezoelectric
crystal is being compressed or pulled, a potential difference is built up on the opposite sides
of the crystal. _______________________________________________________________
__________________________________________________________________________.
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Electricity to Light
 Piezoelectric crystals can produce light ___________________________________________
 Some recent types of flashlights do not have a light bulb. Instead they have ______________
_________________________________________________________________
 LEDs use only a fraction of the power of a traditional bulb and last for years as opposed to
months
Light to Electricity
 The device that is most commonly used to produce electricity from light is called a
photovoltaic (PV) cell, or solar cell.
 PV cells are made of _________________________________________________________.
When light strikes the cell, light is absorbed by the semiconductor material, breaking
electrons loose and allowing them to flow freely
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Topic 5: Portable Power
 An electrochemical cell is an electrical cell consisting of different metal electrodes in a
solution containing an acid or salt.
Electrochemical Cells
 In any electrochemical cell, two metal electrodes are surrounded by an electrolyte, ________
__________________________________________________________________________.
 “Wet cells” use _____________________________________________________________.
 “Dry cells” have ____________________________________________________________.
Figure 3: A Typical Wet Cell Battery
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Figure 4: A Typical Dry Cell Battery
In a typical aluminum-copper wet cell, when the cell supplies current to a circuit, atoms of
aluminum become ions and go into the electrolyte solution.
 This electrode (the negative anode) is consumed as the cell operates.
 The other electrode, the positive cathode, release electrons which are taken up by the
anode.
Very few single cells can produce more than 2 V. To obtain higher voltages, _____________
___________________________________________________________________________
A primary cell is one that __________________________________________.
Rechargeable secondary cells use chemical reactions, which can be reversed.
Fuel cells combine hydrogen and oxygen without combustion. ________________________
__________________________________ are the only by-products of the fuel cell’s reaction.
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Topic 6: Generators and Motors
Electromagnets
 When a soft iron core is inserted into a coil of wire and a current is passed through the wire,
an even stronger temporary magnet called an electromagnet is created.
Factors that Affect the Strength of Electromagnets:
 _________________________________________________________ increase the strength.
 Increasing the current also results in a stronger magnet.
Magnetism to Electricity
 A potential difference (voltage) is “induced” in a wire when __________________________
__________________________________________________________________________.
When the wire is connected to a circuit, an “induced current” flows.
What’s in a Generator?
 A generator produces electric current by __________________________________________
_______________________________ or by ______________________________________
___________________________. As wires in the coil rotate, electrons begin to move along
the wire in one direction.
 After one-half revolution of the wire loop, each side of the coil passes near the opposite pole
of the magnet. This causes the electrons in the coil to start moving in the other direction.
 Electricity produced by this type of generator is called alternating current (AC) because it
changes direction, or “alternates”. Power plants produce alternating current because _______
__________________________________________________________________________.
DC Generators
 A generator that produces direct current is often called a dynamo.
 In a dynamo, the armature (rotating loop of wire) is connected to the outside circuit by a
______________________________________________
 As the armature and commutator rotate, insulating gaps in the commutator momentarily stop
the flow of electric current.
 As the gaps move past the brushes, current resumes but in the opposite direction.
 At this point the direction of charge flow from the armature has reversed but so has the
connection through the commutator.
 As a result, current continues to flow through the load in the same direction.
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Electric Motors: Electric to Mechanical Energy
 A motor uses electric energy to make a coil of wire spin between the poles of a magnet (the
“field magnet”).
 Current flowing through the coil turns it into an electromagnet, which is rotated by magnetic
forces from the field magnet.
DC Motors
 In one common design for DC motors, a rotating wire coil (an armature) becomes an
electromagnet as current flows into it through a split-ring commutator.
 The armature is _________________________________ by stationary field magnets near it,
so it begins to rotate. The commutator acts as a _______________, cutting off and then
reversing the direction of electron flow to keep the armature turning.
AC Motors
 AC motors have a rotation core, rotor, made up of a ring of non-magnetic conducting wires
connected at the ends and held in a laminated steel cylinder.
 Surrounding the rotor is a stationary component called a stator.
 The stator is a two-pole (north and south) electromagnet.
 When an AC motor is turned on, the attraction and repulsion between the magnetic poles of
the stator and the rotor causes the rotor to spin.
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Topic 7: Electricity in the Home
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Transformers are used to “step up” the voltage for efficient transmission over long
distances.
Other transformers “step down” the voltage to the 240/120 V used in homes and factories.
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A fuse contains a metallic conductor that melts when excessive current
heats it up. This opens the circuit until the fuse is replaced.
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A main circuit breaker acts as a switch and safety device that can cut
all power coming into the home.
 If current exceeds a safe level, a bimetallic strip in the breaker heats up, bends, and
opens the circuit.
The individual circuit breakers in the service panel controls branch
circuits located throughout the entire house.
A branch circuit supplies power to one or more wall plugs or lights
connected in parallel by cables in the house walls.
 As additional loads are plugged into a branch circuit, the current
flowing through the connecting cables increases. The small
resistance of the cable wires causes them to heat up when enough
current flows
The breakers, plugs, lights, and switches in each branch circuit are connected by two “live”
wires – a white insulated wire (usually called the neutral wire) and a black insulated wire
(usually called the hot wire). The third wire is the ground wire. It reduces hazards by safely
channeling back into the ground any current that has “leaked” onto metal components in the
electric circuit.
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Digital Devices
 Digital electronic technology – machines that process numerically coded information.
 A Binary code is two states (on or off) that represent numbers and letter.
 Logic circuits containing many switches can process binary information.
 The electronic switches in modern digital devices are transistors, that can be turned on and
off by electric signals.
 Every digital device you use is designed around components that contain enormous numbers
of transistors.
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Measuring Electric Power
 Power is energy per unit of time.
 Electric power describes ______________________________________________________
___________________________________________________________________________
 Electric power can also describe the amount of electric energy that is transferred from one
place to another in a certain amount of time.
power (in watts) =
energy (in joules)
time (in seconds)
– or –
P=
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E
t
One joule per second is also called a _______________
Electric power is not usually calculated directly by measuring energy and time. It is much
more common to measure the voltage and current in a circuit and use these quantities to
calculate power
power (in watts) = current (in amps) × voltage (in volts)
– or –
P=I×V
Example: A current of 13.6 A passes through an electric baseboard heater when it is connected
to a 110 V wall outlet. What is the power of the heater? (1.50 × 103 W)
Example: What is the power (in watts and kilowatts) of a hair dryer that requires 10 A of current
to operate on a 120 V circuit? (1200 W)
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Example: The maximum current that a 68.5 cm television can withstand is 2 A. if the television
is connected to a 120 V circuit, how much power is the television using? (240 W)
Example: A 900 W microwave oven requires 7.5 A of current to run. What is the voltage of the
circuit to which the microwave is connected? (120 V)
Example: A flashlight using two 1.5 V D-cells contains a bulb that can withstand up to 0.5 A of
current. What would be the maximum power of the bulb? (1.5 W)
Paying for Electric Energy
 Most power companies measure electric energy in a customary unit – the kilowatt hour
(kWh).
 One kilowatt hour is the total energy supplied to a 1000 W load during 1 h of operation.
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Solving Cost of Power Problems
1. Determine the # of kW of power used.
2. Multiply the # of kW by the # of hours to get kwh.
3. Multiply the # of kWh by the cost/kWh
Example: A family uses 3000 kWh of electric energy in a two-month period. If the energy costs
11.0 cents per kilowatt hour, what is the electric bill for the period? ($330)
Example: If a refrigerator requires 700 W of power to function, how many kilowatt hours of
power will it require in a 30-day period? (504 kWh)
If electricity costs 11 cents per kilowatt hour, how much would the refrigerator cost to operate in
that period? ($55.44)
Example: A home-owner finds that she has a total of 42 light bulbs (100 W) in use in her home.
(a) If all of the bulbs are on for an average of 5 h per day, how many kilowatt hours of
electricity will be consumed in a 30-day period? (630 kWh)
(b) At 11 cents per kilowatt hour, how much will operating these lights cost the home-owner
during that period? ($69.30)
(c) How much money would the home-owner save if she switched all of the bulbs to energysaving 52 W light bulbs? ($33.26)
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Example: Bob has a stereo that operates at 120 V, using 2.5 A of current.
(a) How much power does Bob’s stereo need to operate? (300 W)
(b) If Bob plays his stereo for an average of 5 h each day, how much electricity will he use in a
30-day period? (45 kWh)
Electric Devices and Efficiency
 If an electric light bulb were perfect, all of the electric energy it took in
(_____________________) would be converted into light (__________________________).
No real device, however, is a perfectly efficient energy converter. Some input energy is
always converted into waste heat.
 You can express efficiency as a percentage using the following mathematical relationship.
efficiency =

useful energy output
× 100
total energy input
To find the efficiency of electric devices, it is often necessary to calculate energy inputs or
E
outputs. To determine the electric energy input of a device, the formula for power (P = t )
can be manipulated to solve for energy.
Efficiency of Common Light Bulbs
 Incandescent bulbs are about ______ efficient, which means about _______ of the input
electrical energy is converted to waste heat.
 Halogen bulbs are filled with high-pressure gas containing traces of iodine
 Halogen bulbs are about _________ efficient,
 Last two to six times longer than incandescent bulbs
 Fluorescent tubes convert about ________ of the total input energy into useful light energy
 Last 10 to 13 times longer than incandescent bulbs, and are much more expensive
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Example: A 1000 W electric kettle takes 4.00 min to boil some water. If it takes 1.96 × 105 J
(196 000 J) of energy to heat the water, what is the efficiency of the kettle? (81.7%)
Example: Find the efficiency of a 23 W fluorescent tube that is used 4.0 h per day and in that
time produces 6.624 × 104 J of useful light energy. (20%)
Example: A 100 W incandescent bulb also produces about 6.624 × 104 J over a 4.0 h period.
What is the efficiency of this bulb? (4.6%)
Example: Based on your answers to the previous two questions, how much money would you
save in a 30-day month if you replaced 25 of the 100 W incandescent bulbs with 23 W
fluorescent bulbs? Assume the bulbs operate 4 h daily, and that electricity costs 10¢ per kWh.
($23.10/month)
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Home Electric Safety
 Do not overload an outlet or a circuit.
 Never work on or clean appliances that are still plugged in.
 Replace frayed or worn out electric cords.
 If the bare wires touch directly (a short circuit), a high current
flows between them, causing sparks and often starting a fire.
 Use receptacle cover on easily accessible outlet.
 Never use appliances close to a sink of bathtub with water in it or
when your hands are wet.
 Ground fault circuit interrupter, a GFCI monitors current flowing
into and out of a load. If any electricity is diverted out of the circuit
wires, the GFIC immediately cuts off the current.
Electric Safety Outdoors
 Never allow your body or something you are holding to come into contact with live electric
wires.
 Never use ungrounded or frayed two-prong electric cords outdoors.
 Do not operate electric equipment outdoors when it is raining.
 Before digging deeply in your yard, make sure that there are no underground utility cables.
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Topic 8: Electricity Production and the Environment
Electric Energy from Burning Fuels
 Fuel oil, natural gas, and coal, are burned in large __________________________________
___________________________ to produce about one quarter of our country’s electricity.
Fossil Fuels Affect Land and Air
 Open pit mining of surface deposits disturbs soil and vegetation.
 Underground mines produce waste materials called “tailings,” which accumulate near the
mine.
 Water seeping through the tailings becomes ______________________________________.
 When fossil fuels are burned, contaminants such as visible particles and invisible gases
escape form smokestacks.
 ___________________________________________ can remove most of the solid particles.
 Scrubbers can remove sulfur dioxide. Scrubbers spray a water solution through the waste
gases. SO2 and other pollutants react with chemicals in the water and are removed.
 Complete burning of pure coal or natural gas would produce _________________________.
 Carbon dioxide is a greenhouse gas, which means that it helps delay the escape of heat from
Earth’s atmosphere. This could lead to a rise in the average temperatures on Earth- global
warming.
 Natural gas _________________________________________________________________
__________________________________________________________________________.
Electric Energy from Flowing Rivers
 Hydro-electric plants use water pressure to generate electric energy. Hydro-electric power
plants appear to be a very clean form of electric energy generation. However, reservoirs,
which store behind the dams, __________________________________________________.
Homes, small villages, and even entire towns may need to be moved, displacing people and
industries.
 When submerged vegetation decays, micro-organisms responsible for this process use up the
oxygen supplies in the water.
 Sometimes decaying matter produces methane gas
 Other forms of life, such as algae, take over and change the ecosystem.
Energy From Atomic Reactions
 Bombarding uranium atoms with tiny particles called neutrons causes the uranium to split
into two smaller atoms.
 In the process called _____________________________, a tremendous amount of energy is
released. This is referred to as __________________________________________________.
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Fission reactors do not release soot or gases that cause acid rain, nor do they release
greenhouse gases. However, used (spent) reactor fuel is _____________________________
________________________________________________________
The reactors themselves also become slightly radioactive so they are difficult and expensive
to decommission.
In the Sun and other stars, nuclear fusion joins very small atoms to form a larger atom.
Huge amounts of energy are released in this process
Developing technology to create and use continuous controlled fusion as a power source is an
extremely difficult and expensive project.
Heating the Environment
 All thermonuclear and thermo-electric-generating plants release thermal energy into the
environment.
 Thermal pollution occurs when this warm water is returned directly to the lake or river from
which it is taken, increasing the water temperature. Even a change of a few degrees can
affect the plant and animal life in the water.
 To reduce thermal pollution, large generating plants have cooling ponds or towers where
waste water can return to the temperature of the surroundings before it is released.
Cogeneration
 It makes environmental sense to design electricity-generating stations as cogeneration
systems that produce electricity and also supply thermal energy, such as hot water or steam,
for industrial or commercial heating.
Alternative Energy Sources
 Energy from the Sun, wind, and tides, which until now has been too expensive or too
difficult to harness, is rapidly becoming competitive with conventional energy sources.
 Wind-driven electricity generation must be used together with other electric energy sources
or storage devices.
 Solar-powered-generating systems often include storage batteries to supply electricity at
night or in cloudy conditions.
 Ocean tides are another source of energy that can be used to generate electricity.
 The hot inner parts of the Earth contain a great deal of thermal energy, called geo-thermal
energy. Ground water flows down from the surface, absorbs thermal energy, and rises again
as hot spring and geysers. Steam produced by geothermal activity can be used to rotate
turbines and turn electric generators.
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Sample PAT Questions (from 2008 and 2010)
1. When clothes are removed from a clothes dryer, sparks can be seen as the clothes are
separated. These sparks are a result of
A. current electricity
B. an electrical discharge
C. a buildup of neutral atoms
D. anti-static sheets absorbing neutral charges
Use the following information to answer the next question.
Facts About Electricity
I
II
III
IV
Electrons can be discharged when clothes are removed from a clothes dryer.
Electrons flow continuously through a conductor.
Electricity can be used to operate a motor.
Electricity can build up and produce lightning.
2. Which facts describe properties of static electricity?
A. I and III
B. I and IV
C. II and III
D. II and IV
Use the following information to answer the next question.
3. The total electrical energy consumed by Joe’s television is
A. 33.3 J
B. 108 J
C. 1.20 kJ
D. 4.32 MJ
Page 23 of 31
Use the following information to answer the next question.
4. Which change could Roger make to the wet cell to produce electricity?
A. Replace one of the zinc electrodes with copper.
B. Increase the sulfuric acid concentration to 7.5%.
C. Replace both of the zinc electrodes with copper.
D. Decrease the sulfuric acid concentration to 2.5%.
Use the following information to answer the next question.
5. The total electrical energy consumed by Joe’s television is
A. 33.3 J
B. 108 J
C. 1.20 kJ
D. 4.32 MJ
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6. Which of the following sequences shows the transfer of energy initiated by the flow of water
in a hydroelectric power plant?
A. Mechanical-gravitational-electrical
B. Electrical-gravitational-mechanical
C. Gravitational-electrical-mechanical
D. Gravitational-mechanical-electrical
7. Which of the following modifications to an electromagnet will increase its strength?
A. Using a larger iron core
B. Using fewer coils of copper wire
C. Increasing the resistance of the iron core
D. Decreasing the current passing through the coils of copper wire
8. Which of the following sets of components in a series circuit would cause the light bulbs to
shine the brightest?
Row
Resistance
Load
Resistor present
2 bulbs
A.
Resistor present
3 bulbs
B.
C.
No resistor present
2 bulbs
No resistor present
3 bulbs
D.
Use the following information to answer the next question.
A student explains how electric circuits function by comparing them to a traffic model. Some of
the components of traffic are listed below.
I
II
III
IV
Traffic Components
Road construction sites
Stop signs
Vehicles
Roads
9. Which component of the traffic model is most closely related to switches found in circuits?
A. I
B. II
C. III
D. IV
Page 25 of 31
Use the following information to answer the next question.
10. Which of the following diagrams represents the circuit described above?
11. Which of the following sources of energy is classified as renewable ?
A. Natural gas
B. Biomass
C. Coal
D. Oil
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12. Which of the following wet cells would produce the highest voltage?
Use the following information to answer the next question.
13. To the nearest tenth of a watt, how much power does the bulb consume (P = IV)?
A. 0.5 W
B. 2.0 W
C. 13.4 W
D. 39.6 W
Page 27 of 31
Use the following information to answer the next question.
14. The resistance in the circuit shown above is
A. 2 Ω
B. 3 Ω
C. 4 Ω
D. 6 Ω
15. Tungsten is used as a filament in some light bulbs because it
A. allows electrons to flow easily
B. allows protons to flow easily
C. resists the flow of electrons
D. resists the flow of protons
16. A disadvantage of hydroelectric power generation is that it
A. emits pollutants into the atmosphere
B. disrupts the natural flow of waterways
C. provides an unreliable method for producing energy
D. produces hazardous waste that requires long-term storage
Page 28 of 31
Use the following information to answer the next question.
17. Which of the following statements predicts the relative brightness of each of the three light
bulbs in the circuit shown above?
A. Light bulb 1 is dimmer than light bulb 2, which is dimmer than light bulb 3.
B. Light bulb 1 is brighter than light bulb 2, which is brighter than light bulb 3.
C. Light bulb 1 is dimmer than light bulbs 2 and 3, which both have the same brightness.
D. Light bulb 1 is brighter than light bulbs 2 and 3, which both have the same brightness.
Use the following information to answer the next question.
18. Which motor component functions as an electromagnet?
A. Permanent magnet
B. Power source
C. Commutator
D. Armature
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Use the following information to answer the next question.
19. Which component in the circuit shown above is protected by the circuit breaker when both
switches are closed?
A. Furnace motor
B. Exhaust fan
C. Heater
D. Light
20. An electrical device with low efficiency is most likely to produce excess
A. heat energy
B. light energy
C. sound energy
D. mechanical energy
Page 30 of 31
Use the following information to answer numerical response question 1.
Kelly recorded the input energy and output energy of four electric devices.
Device
1
2
3
4
Input Energy (J)
10
71
100
950
Output Energy (J)
3
16
27
510
Numerical Response
1.
When listed in order from the most efficient device to the least efficient device, the order is
_____________,
Most efficient
_____________,
_____________,
and
_____________
Least efficient
Use the following information to answer numerical response question 2.
In order to produce 100 000 J of heat energy, a hot plate consumes 800 000 J of electrical
energy.
Numerical Response
2.
To the nearest tenth of a percentage, the efficiency of the hot plate is _____________%.
Answers:
1. B
2. B
3. D
4. A
5. D
6. A
7. A
8. B
9. C
10. B
11. D
12. A
13. C
14. D
15. C
16. B
17. B
18. D
19. A
20. A
NR1. 4132
NR 2. 12.5
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