1
Unit 3 The Characteristics of Electricity ( pg 296 )
Day 1
______________- study of static electricity
_____________ - materials that do not carry a charge
______________ allow charges (electrons) to flow through them easily. E.g. _______________________
Therefore no matter how hard that you rub a metal tap no static charge will build up because the electrons
that you are giving the tap just keep on moving up the tap and down the water line until they reach a
ground.
____________do not allow charges to flow through them. The charge builds up on its surface eg.
_______________ Both a positive and a negative charge can build up on ____________________
Only ______________ can obtain a static charge.
Conductors, Insulators and in – between (pg 308)
Conductivity is the ability of materials to allow electrons to move freely in them. Materials that hold onto
their electrons and do not allow them to move easily are called electrical insulators.An electrical insulator
is a solid, liquid, or gas that resists or blocks the movement of electrons. Dry wood, glass, and plastic are
all examples of electrical insulators. An insulator can hold a static charge because static charges remain
nearly fixed in place.
Since electrons cannot move through an insulator they can be very useful to us to protect us from shocks.
For example a simple electric kettle would be very hazardous if the two wires that supplied electricity to it
did not have a rubber coating over them
See Table pg 308 for some common insulators and conductors.
___________________ are good conductors since e’s can jump from one atom to the next
_________________ are insulators since they hold their e’s tightly
Why do you get more shocks in the winter than in the summer?
-
This is because in winter the air is far dryer than in the summer and dry air is an ______________ and
therefore does not take any of the charges our body might pick up during the day. So when we go and
touch another conductor (a door handle) ZAP we receive a shock.
2
The Electrical Nature of Matter pg 301
electric charge- can be positive or negative
_____________- they have an even number of positives and negatives
an object has a ____________charge if it has more negatives than positives
an object has a _____________charge it it has fewer negatives than positives
The Law of Electric Charges- like charges ____________one another, unlike charges ____________ one
another, charged objects are attracted to uncharged objects
A Model for the Electrical Nature of Matter : The atom is composed of electric charges.
Protons –____________charge, found in nucleus, cannot move
Neutrons- _______________charge, found in nucleus, cannot move
Electrons- _______________charge, found orbiting nucleus, can move from atom to atom
A model for the electrical nature of matter.
1.
2.
3.
4.
5.
6.
7.
All matter is made up of submicroscopic particles called ______________.
At the center of each atom is a ___________, with two kinds of particles: the positively charged
_____________and the uncharged _____________. ___________ do not move from the nucleus when an
atom becomes charged
A cloud of negatively charged particles called _____________ surround the nucleus. An electron has the same
amount of charge as a _______________, but the kind of charge is ________________. When atoms become
charged, only the _________________ move from atom to atom.
___________charges repel each other; _______________ charges attract each other.
In some elements, such as copper, the nucleus has a weaker attraction for its electron than in others, and
electrons are able to move freely from atom to atom. In other elements, such as sulfur, the electrons are
strongly bound to each atom.
In each atom, the number of electrons surrounding the nucleus equals the number of _______________ in
the nucleus. A single atom is always electrically neutral.
If an atom gains an extra electron, the net charge on the atom is ________________, and it is called a
________________ ion. If an atom loses an electron, the net charge on the atom is
____________________and it is called a _________________ ion.
Charging by contact (Friction) pg 302
When two objects made of different materials rub together, electrons can be transferred from one object to the other.
This is because different atoms (which make up the objects) have a different ability to attract electrons and a different
ability to hold onto their own electrons.
3
The Electrostatic Series
-a list of common materials showing how their ability to hold onto their electrons compares
acetate
glass
wool
fur, hair
calcium, magnesium, lead
silk
aluminum, zinc
cotton
paraffin wax
ebonite
polyethelene (plastic)
carbon, copper, nickel
rubber
sulphur
platinum, gold
Weak hold on electrons
Strong hold on electrons
To determine what charges will form, compare the location on the table of the two objects. The object that is higher
on the table will ______________ electrons and become _________________. Eg. when cotton and human hair rub
what charge will form on each object? ___________ is lower on the list than ___________. __________ will hold its
electrons better. ____________ will lose its electrons to the ________________Cotton will become
___________. Hair will become ________________Consider the following pairs are rubbed together. Give
charge on each : Plastic ________ Silk _______; Fur __________ Rubber ; glass ____ silk ______
Vinyl ______ Plastic ______ ; Ebonite _________ wool _____________
Questions
1. Where are electrons in the atom?
2. What does “static” mean in “static electricity”?
3. What happens when two objects made out of different materials are rubbed together?
4. What term describes an atom’s tendency to hold on to electrons?
5. In each of the following pairs, state which one is more likely to give up electrons.
(a) wood or human hair
(b) plastic wrap or steel
(c) cotton or silk
Complete pg 300 ( 1-4 ) pg 306 (1-5 )
4
Day 2 Induction (pg 303)
Charging by induction- charging without direct contact
When a negative charge approaches a neutral object, the electrons inside the neutral object are
_____________. This causes an induced __________ charge on the side closest to the negative object
and an induced ___________ charge on the opposite side.
Diagram
When a positive charge approaches a neutral object, the electrons inside the neutral object are
____________. This causes an induced __________ charge on the side closest to the positive object
and induced __________charge on the opposite side.
diagram
If a ground is attached to the neutral object, electrons can flow into or out of it to make it “feel” neutral.
Diagram
Induction is used in photocopiers, lightning, dust filters and electrostatic painting.
CHARGE BY INDUCTION
-no direct contact (e- move within a substance because of nearby objects)
(-) object goes near neutral object, (-) charge is repelled, (+) charge is attracted in neutral object
(+) charge is induced by (-) object
(+) object goes near neutral object, (+) charge is repelled, (-) charge is attracted in neutral object
(-) charge is induced by (+) object
1.
2.
Draw the normal spread of negative
charges on this piece of tissue (a
neutral object)
Draw the build-up of negative
charges on this balloon, AFTER it
has been rubbed with a cloth
3.
4.
The tissue is now stuck to
the balloon. Draw the
charges as they now
appear.
Draw the same balloon as in stage 1.
Draw the charges in the tissue paper
so that all the negative charges are
far away from the negative charges
on the balloon. As they get closer
together the tissue is attracted to the
balloon
5
When a neutral object is given a temporary charge, this is called _____________. If the object with a
temporary charge is light enough it can be _____________ towards the object that caused the temporary
charge.
Conclusion : objects charged by induction receive the _________________ charge to the charged object ;
in the case above it is temporary ; the charge can become permanent if grounding is used.
GROUNDING -earth is large and absorbs large numbers of electrons, ground wire is connected to earth to
"dilute"the charge by carrying it to the earth
1.
2.
Rub one end of the polyethylene strip with fur. Mount the strip on an evaporating dish..
Rub one end of another polyethylene strip with fur. Bring this charged end of the strip close to, but not
touching, the charged end of the strip on the dish. (a) Record your observations.
____________________________________________________________________________________
3.
4.
5.
Bring the uncharged end of the polyethylene strip close to the charged end of the polyethylene strip on the
dish.(a) Record your observations. ____________________________________________________________
Repeat steps 5, 6, and 7, but substitute acetate strips that have been rubbed with silk. (a) Record your
obervations. ________________________________________________________________________
Charge a polyethylene strip with fur and mount it on the dish. Charge one end of an acetate strip with silk,
and bring it near e charged end of the polyethylene strip in the dish. a) Record your observations.
_______________________________________________________________________
CHARGE BY CONTACT
-rub material to build up electrons on object (-) or lose electrons from object (+)
(+) object touches neutral object and takes e-, both objects now have e- spread out, both are (+)
(-) object touches neutral object and gives e-, both objects now have extra e-, both are (-)
Balloon and cloth BEFORE being rubbed
together
r
Balloon and cloth AFTER being rubbed
together
The negative charges will jump from the places where there are the most number to where there are the least.
Complete the following diagrams by adding negative charges (electrons) or a static electricity spark:
a.
b.
c.
d.
6
Negative charges (or electrons) will always move from where there are the (greatest/fewest) number to
where there are the (greatest/fewest) number. If there is a big enough difference and the two objects are
close enough together, this jumping may cause a ____________. . see page 309. Where we see the
greatest spark when the air is dry or when there is high humidity ? _______________________________
Conclusion : charging by contact the neutral object becomes the _________________ charge as the
charging object.
Transferring Charge by Contact

sparks produced by a charge transferred by contact can be dangerous

transferring a charge by friction is difficult to avoid; when charging by contact occurs, one object is
already electrically charged

the other object may or may not be charged, the important factor is that
there is a DIFFERENCE in the charge on the two objects
7
Day 3
PITH BALL ELECTROSCOPE LAB
Purpose: To use a pith ball electroscope to determine charges.
Materials and Methods:
1. Bring a negatively charged ebonite rod close to (don't touch) the uncharged pith ball, and then
remove it.
2. Repeat step 1 with a positively charged acetate strip.
3. TOUCH the uncharged pith ball with a charged ebonite rod, remove the rod, and then slowly
APPROACH (don't touch) with the same charged ebonite rod. Now APPROACH (don't touch) with a
charged acetate strip.
4. Gently touch the pith ball with your fingers to "ground" (discharge) it.
5. TOUCH the uncharged pith ball with a charged acetate strip, remove the strip, and then APPROACH
(don't touch) with the same charged acetate strip. Now APPROACH (don't touch) with a charged
ebonite rod.
Observations:
step 1
step 2
step 3
step 5
Questions: (Answer on a separate sheet)
1. Draw a neat, well-labelled diagram (in pencil) to illustrate each of the following. In each diagram,
label the pithball electroscope, fur or plastic, ebonite rod, positive and negative charges that do or
don't move, any movement of pith ball.
a)
How to charge an ebonite rod negatively.
b) How to charge a pith ball electroscope negatively with an ebonite rod.
c)
How the pith ball electroscope reacts to an ebonite rod after both have been charged
negatively and the rod is brought close.
2. What charge is transferred to the pith ball when an ebonite rod rubbed with fur is touched to it?
How do you know the charge you indicated was transferred (ie. think of how the pith ball reacts
when the rod is brought near it after contact). Are electrons moving from the rod to the pith ball or
from the pith ball to the rod?
3. What charge is transferred to the pith ball when a acetate rod rubbed with silk is touched to it?
How do you know the charge you indicated was transferred (ie. think of how the pith ball reacts
when the rod is brought near it after contact). Are electrons moving from the rod to the pith ball or
from the pith ball to the rod?
4. Define the "Law of Attraction and Repulsion" (pg. 301).
5. In step 4 you "grounded" the pith ball electroscope by touching it with your fingers. Read the
section on GROUNDING in your text and briefly explain the process (pp. 311-312).
8
Day 4
INDUCTION LAB: METAL LEAF ELECTROSCOPE
Purpose: To charge a metal leaf electroscope by induction.
Materials and Methods: (If at any time the leaves stick together, touch the metal ball with
your fingers and use a pencil to GENTLY separate the leaves)
1. Observe the metal leaves of a neutral electroscope noting their position.
(Make a sketch of the electroscope and leave room to add labels and charges later)
2. Approach the metal ball of the uncharged electroscope with a negatively
charged ebonite rod (do not touch the electroscope) and observe the leaves.
(Make a sketch of the electroscope with the rod close and leave room to add labels
and charges later)
3. Repeat with a positively charged acetate strip.
(Make a sketch of the electroscope with the rod close and leave room to add labels
and charges later)
4. Connect one end of an insulated wire to the neck of the electroscope just under
the metal ball. Connect the other end of the wire to a metal water tap or gas valve.
Bring a negatively charged ebonite rod near (do not touch) the ball of the
electroscope. While the rod is still very close to the electroscope, remove the wire
from the water tap or gas valve without touching any part of the electroscope.
After you have done this, remove the charged rod and observe the leaves.
(Make a sketch of the electroscope with the wire still attached but showing the
final position of the leaves once the rod has been removed and leave room to add
labels and charges later)
9
Questions: (Answer in full sentence on separate page)
1.
Explain what happened in step 2 in terms of the movement of electrons. Explain why the
leaves did what they did.
2.
What kind of charge was induced on the metal-leaf electroscope by the ebonite rod?
3.
Explain what happened in step 3 in terms of the movement of electrons. Explain why the
leaves did what they did.
4.
What kind of charge was induced on the metal-leaf electroscope by the acetate strip?
5.
Explain what happened in step 4 in terms of the movement of electrons. Explain why the
leaves did what they did.
6.
Write a summary statement identifying the kind of charge (positive or negative) transferred
to an object when it is charged by induction by an ebonite rod and by an acetate strip.
10
Charging Neutral Objects By
Induction
1. Only applies to charging
metals!
2. Charge is induced on the object
without direct contact.
3. The object takes on the opposite
charge of the rod or other object
being used to induce a charge.
Rod (+)  Object (-)
Rod (-)  Object (+)
Scenario #1 – Charging Using a
Positive Rod
Step 1:
Start with a positively
charged rod (+).
Step 2:
Approach the positive rod to the object (+) without touching it.
Step 3:
Electrons inside the object are attracted to the rod. Only the electrons move closer to the
rod but they do not jump.
Step 4:
Add a grounding wire but keep the negative rod close to the object.
Results:
The electrons from the ground enter the object (opposite charges attract)
Step 5:
Remove the grounding wire first. Pull the rod away second.
The object is now permanently charged by induction
and it has become negatively charged.
Scenario #2 – Charging Using a Negative Rod
Step 1:
Start with a negatively charged rod (-).
Step 2:
Approach the negative rod to the object (-) without touching it.
Step 3:
Electrons inside the object are repelled by the rod. Only the electrons move away from the
rod but they do not jump out of the object.
Step 4:
Add a grounding wire but keep the negative rod close to the object.
Results:
The electrons from the object are repelled and move down the wire and into the ground
(like charges repel).
Step 5:
Remove the grounding wire first. Pull the rod away second.
The object is now permanently charged by induction
and it has become positively charged.
11
watch on youtube : What is Static Electricity ? ( Animation )
go to http://www.stmary.ws/highschool/physics/home/review/StaticElectricityReview.htm try animations
12
Key Concept Review
1. (a) Draw a diagram of an atom that has four protons, five neutrons, and four electrons.
(b) Label each particle with its name and whether it is positive (+), negative (–),or neutral.
2. (a) What is friction?
(b) Explain how friction can be used to transfer electrons. Use two substances from the triboelectric
series in your answer.
3. Explain why this statement is false: “A neutral object contains no charge.”
4. State the two laws of static electric charges.
5. Where are static charges held?
6. Why might a plastic rod that contains a large number of electrons not have a static charge?
7. (a) What is the difference between a conductor and an insulator?
(b) What is an example of a conductor?
(c) What is an example of an insulator?
8.Do two identical objects become statically charged when you rub them together? Explain why they do or
do not.
9. What does an electroscope detect?
10. In the contact method of charging, what charge does a neutral substance gain compared to the object
that touched it?
11. In induction, what charge does a neutral substance gain compared to the object brought near it?
12. What is the difference between charging by contact and charging by induction in terms of electron
transfer?
13. What is grounding?
13
Day 5
LIGHTNING
(pp. 313-315)
Strong ___________ and the collision of ___________ _____________ and ___________
_______________ in the clouds strip ___________________ from some particles and deposit them on
others. Strong updrafts in the _______________ of the ___________________ carry smaller
____________ crystals and particles up while larger ones fall down. __________________ charges collect
at the ________________ of the clouds whereas the higher, ________________ parts of the clouds are
_________________ charged.
The negative charges on the ___________________ of the clouds repel _________________ on the
surface of the ___________________, leaving the ground _________________ charged just below the
cloud. This is an example of charging by ___________________ (contact? friction? induction?). The strong
_____________________ between the __________________ cloud and the ____________________
ground pull ___________________ off atoms and molecules in the air. This occurs mostly over the
_____________________ point on the ground.
A chain of ______________ forms and a gigantic ___________________ occurs between the
_________________ and the ____________________. So many ___________________ crash through the
air so fast, colliding with other _____________________, that the air both __________________up and
__________________ up (ie. the temp. can reach ____________________ near a lightning bolt). The heat
causes the air to __________________ rapidly. ______________ molecules colliding with other
____________ molecules produce a _____________ wave that we hear as _____________________. If
the lightning hits a person, it can stop the ___________________ or _______________________.
The best way to control a lightning strike is to direct the flow of _______________ away from buildings
and prevent fires. Electrons travel most easily through ___________________. ___________________
rods are based on this principle.
A lightning rod is charged by ___________________, just like the sphere on your ___________________.
The _______________ charged lightning rod is the ____________________ point in the area. It attracts
the ____________________ ions that have formed in the ______________, while the cloud attracts the
___________________ ions. A chain of ____________ thus forms between the cloud and the lightning
rod. This chain acts as a ____________________ providing a path for the __________________
_________. When the lightning bolt strikes, it hits the ___________________ __________. The
____________________ are carried into the _________________ by a heavy conductor, often made of
braided ________________.
Although the light from lightning travels so fast it almost takes no time to reach us. But the sound from the
thunder takes about __________ seconds to travel one _________________. Imagine you heard thunder
six seconds after you saw a lightning flash. How far are you from the lightning bolt? ___________ km.
-
watch video www.teachersdomain.org
Electricity And Magnetism: Lightning
Lightning and Electricity And Magnetism: Lightning
14
Van de Graaff Electrostatic Generator
The American physicist Robert Jemison Van de Graaff invented the Van de Graaff generator in 1931. This
device has the ability to produce extremely high voltages (as high as 20 million volts).
When the motor is turned on, the lower roller (charger) begins turning the belt. Since the belt is made of
rubber and the lower roller is covered in silicon tape, the lower roller begins to build a negative charge and
the belt builds a positive charge.
As long as there is air between the lower roller and brush assembly, the Van de Graaff generator will
continue to charge the belt. Theoretically, the Van de Graaff generator can continue to charge forever.
Unfortunately, dirt and other impurities in the surroundings will limit the actual charge that develops on the
sphere.
-
watch video on youtube : Bill Nye The Science Guy on Static Electricity (Full Clip)
15
SNC1D
Name _______________________________
Static Electricity Assignment: The Practical Use of Static Charges
You have now seen three different ways that static charges can be gained by substances:
1. Friction – in which the charge given is determined by the electrostatic attraction the two substances
have, the one with the greater attraction becoming negative and the one with the weaker attraction
becoming positive
2. Contact – in which the charge given is the same as the charge on the charging object
3. Induction – in which the charge given is opposite the charge on the charging object.
Much of our discussion of Static Electricity has focused on some of the negative effects (lightning strikes,
and shocks for instance). This assignment deals with some of the more positive uses of static charges.
Photocopying
Many people are unaware of the fact that common photocopy machines make use of static electric effects.
While the motors and lamps within the photocopier work on current electricity ( the topic of the 2 nd part of
this unit) the photocopy process itself uses static charges.
16
Summarize the process by completing the following (read page 310 in your text)
Inside a photocopier…
1. A bar rubs up against a selenium coated drum in order to ____________________________________
2. A light shines on the page to be copied. This creates an image which is projected onto the selenium
drum by using both a _________________ and a __________________.
3. The bright light hits the drum and causes the charges to _______________________. The shadow
areas (areas not affected by the light, remain __________________ charged.
4. In the toner cartridge of the photocopier, negatively charged toner is picked up by a brush. As this
brush comes into contact with the selenium drum it sticks to the drum because __________________
5. Paper from the paper tray is given a ______________________ charge. As this paper rolls under the
selenium drum it transfers its ______________________ onto the paper.
6. The paper is then heated with a lamp to ____________________________________
In this space summarize the following uses of static electricity
Electrostatic precipitators
_______________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Electrostatic spray guns
________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________________
Try this on your own!

You can demonstrate the usefulness of static forces with a simple experiment described in your text.
On a sheet of paper, sprinkle a few grains of salt and pepper. Using a plastic ruler and a wool sweater,
charge the ruler by friction. Hold the ruler over the mess you made on the paper, and you can
demonstrate the essential elements of an electrostatic cleaner.


Which of the two, salt or pepper is attracted to the ruler?
Can you see how this fact could be used in more practical applications?
17
Electrical Discharging( pgs 311-312 )
-
When a charged object has its charge removed it is said to be discharged or ______________
-
The simplest way to discharge something is to __________it. This means to connect it to the Earth
by means of a ______________.
-
When a charged object is grounded it shares its whole charge with the Earth, and since damp soil is a
fairly good conductor the charge spreads out over the whole surface.
-
Since the Earth is so large it effectively removes all the excess charge given to it
-
Examples: Lightning rods, gas pumps
-
You can also discharge an object at a point. Conductors that are shaped into a point at one end loose
their charge extremely fast because there is a build up of negative charge in a very small surface so the
electrons are repelled right out of the conductor.
-
Discharging at a point is an extremely effective way for airplanes to get rid of their charge since
attaching them to a ground just wouldn’t be practical.
-
A third way an object will discharge is just letting it sit, over a period of time the charge will leak out of
it into the water molecules in the air.
Independent Research
analyse the design of a technological device that improves its electrical efficiency or protects other devices
by using or controlling static electricity (e.g., paint sprayers, photocopiers, lightning rods, grounding wires)
Questions:
How does eliminating static electricity help or hinder the performance of a device?
How have static electricity controls helped in developing new technologies?
-
Complete pg 318 (1-4) pg 320 (1-18), 21,22,24,28,31,32
18
Day 6 Electricity and Electric Circuits p. 324
Electric current: The movement or flow of electric charges from one place to another.
Electric circuit: A controlled path for electrons to flow through.
The 4 parts of an electric circuit:
1.
Source of Electrical Energy- eg. solar cells, batteries, wall outlets
2.
Electrical Load- anything that converts electrical energy into another form of energy eg. lamp,
motor
3.
Electric Circuit Control Device- turn flow on or off eg. timer, switch, fuse, circuit breaker
4.
Connectors- allow electrons to flow from part to part eg. wires
Schematic diagrams
o
Use circuit symbols instead of drawings of components
o
Simpler to read, no artistic talent needed.
o
Universal method of communicating circuits.
Copy the symbols on pg 324 /600 used to represent the following components of a
circuit:
Part
Cell
3 cell
battery
Wall outlet
Switch
Fuse
Resistor
Light bulb
Symbol
Function
Part
Voltmeter
Ammeter
Conducting
wire
Ground
connection
Symbol
Function
19
Water Flow Analogy
Electric Circuit
Electric Current pg 325
Electric Current
Definition
Symbol
SI unit
Measuring device
Safety
a measure of the rate at which charges move past a certain point in a circuit
________________
________________
Ammeter connected in _____________(pg 600)
The more current, the more electrons that travel into you, the more damage
that can occur. Current causes your heart to stop beating.0.005 A is maximum
safe amount of current
Compared to water
Water in a river vs water in a stream. They may both move at the same speed
(energy) but the river has more potential to do work because there is more
water in it (more current)
- one ampere = 1 coulomb of electrons per second passing a given point in a circuit
18
- a coulomb is 6 241 460 900 000 000 000 electrons or 6.241 x 10
- an ammeter is the instrument used to measure current
- ammeters are always connected in series within a circuit
The flow of current from batteries direct current (DC)because the current flows in only one direction but
the current that flows through cords plugged into the wall sockets in your home is called alternating
current. Alternating current (AC) flows back and forth at regular intervals called cycles. This is the
current that comes from generators and is carried by the big power lines to your home.
Electric Potential pg 330
Definition
The energy difference between electrons at two locations in a circuit
Symbol
SI unit
Measuring device
Safety
___________
___________
Voltmeter connected in __________________________ (601)
The higher the voltage, the more energy electrons can release. This can
result in burns when they release heat energy.
A waterfall has potential energy that is transferred to the water to make a
river run. If the river looped back to the waterfall, a complete circuit
would be made. The water is like electrons.
Compared to water
20
- electric potential is measured in volts and electric potential is often called voltage (symbol V)
- a voltmeter measures the electric potential of a source of electrical energy
- voltmeters are always connected in parallel with a load (because without a load there is no drop
in voltage)
Connecting a voltmeter in parallel
A model of electric potential
Analogy
 Falling water used to turn water wheels
 Falling water gives up gravitational potential to turn the wheel
 electric charges released from a dry cell give up their energy to turn the electric motor
 Pump has lifted water to the top of the building, water has some stored, or potential energy
 As long as the pump inside the building gives the water at the bottom potential energy by
pumping it back up to the top, it will again fall from the top of the building to continue turning the
wheel
 dry cell gives a huge amount of electric charges (electrons) a certain amount of electric potential
energy
 the energy each electron gains is released to it by the chemical reactions that occur
 electrons have electrical potential energy at the ______________terminal of a dry cell
Electricity from Chemical Reactions
 Even if dry cell is not connected to a circuit, the stationary electrons at the negative terminal have
electric potential energy.
 Chemical reactions occur and exert a force on the electric charges that pushes a certain number
of them on to the terminals of the dry cell.
 An excess of electrons accumulates on the negative terminal, thus giving it a negative charge and
a matching amount of positive charges remain on the positive terminal
 Electrons are released with electric potential energy when the switch is closed
As the electrons move through the circuit, they release the energy to the electrical load in the circuit
Complete pg 329 (1,2,4,5) pg 336(1-5)
21
Day 7 Electrochemical Cells pg 383
-
electrochemical cells are also known as _______________ cells or ___________________ cells
In 1800 ________________________ invented the first battery
ELECTROCHEMICAL CELLS -stored chemical energy is converted into ________________energy ;
consists of ____________________ and an ___________________________
PRIMARY CELLS (disposable energy)
electrical current flows from primary cells, and chemical reactions occur, using up some material
-when all material is discharged, primary cell is used up
(a) VOLTAIC CELLS - non-rechargeable primary cell
-two pieces of ____________ (electrodes) placed in liquid (_________________________)
ELECTRODE -electrical conducting plate in solution eg. Al, Cu
ELECTROLYTE -liquid that conducts electrical current eg. H2SO4
See diagram fig 12.3 page 383
-
electrons flow from the __________________ to _______________________ through the
___________________________ __________________
-
the aluminum electrode is called the anode and has a neg. charge
-
aluminum atoms lose __________________ and become ______________________
-
over time the aluminum electrode will get __________________________
-
at the copper strip which is called the cathode and has a positive charge ______________ ions pick
up electrons forming __________________ gas
Do lab activity pg 384. Copy out chart pg 384
22
Post Lab
1.
Copper strip – evidence of a chemical reaction : formation of _________ ___________
2.
As time passed booth the voltage and current __________________________
3.
Potential difference was effected when a) aluminum was used instead of ____________ and when
___________________ metals were used
Current – removing bubbles _______________ current and decreasing surface area of the
electrodes ______________________ the current.
4.
Potential difference – combination of __________________ used and the length of time cell
operated
5.
Current was increased when the surface area of the metals was ________________ and when the
bubbles of gas were ____________________.
6.
Largest current was when the whole electrode was submerged and only a few bubbles were
present.
7.
_________________ and zinc produced the greatest potential difference
8.
In designing a voltaic cell electrodes of _______________ and _________________ should be
used and immersing them ________________ in the liquid. To increase the life of the cell
_______________ the surface area of the electrodes.
-
car battery is good example of a wet cell ; the negative electrode is made of _____________ and
positive electrode is made of ___________________; the electrolyte is _____________________
-
it is called a ______________________ cell since it can be recharged
Disadvantages of using Wet cells :
-
the ________________ electrode is used up
-
bubbles of ________________ gas form on the __________ electrode reducing __________ flow.
-
_____________ gas is very _________________________
-
the electrolyte __________________ acid is very _________________; may _________________
or ___________________.
(b) DRY CELLS (pg 387)
-
works like a wet voltaic cell, but electrolyte is a ___________ or a ________(not a liquid)
advantages = less chance of spilling electrolyte ; explosive hydrogen gas is not produced
-
negative terminal is made of ________________________
-
positive terminal is a __________________ rod surrounded by ______________________
-
separating the 2 electrodes is a paste made of ______________, _______________ and
____________________.
-
2 disadvantages : ______________________ and _________________________
23
Day 9
Lab : Building Batteries ( pg 390 )
Voltage
Brightness of Bulb
One Cell
2 cells in series
3 cells in series
2 cells in parallel
3 cells in parallel
Analyze :
1.
_____________________________________________________________
______________________________________________________________
2.
______________________________________________________________
______________________________________________________________
3.
______________________________________________________________
______________________________________________________________
Conclusion :
4.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
5.
_________________________________________________________________________
_________________________________________________________________________
6.
_________________________________________________________________________
_________________________________________________________________________
7.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
24
Cells in Series and Parallel
Cells in Series
series circuits – one pathway for electrons, connected so that _________terminals touch
_________terminals
parallel circuits – more than one pathway for electrons, connected so that negative terminals
touch _____terminals
-
As electrons travel through each new battery, they get a new boost of energy.
Eg. If three 1.5 volt cells are connected in series, electrons receive 1.5V from each cell.
1.5 + 1.5 + 1.5 = 4.5V total
This is similar to water travelling down subsequent waterfalls. As it falls over each one, the water
travels faster.
 Water analogy: to get twice as much energy from the same amount of water, we would lift the
water twice as high and double the gravitational potential energy
Cells in Parallel
o
Electrons only travel through one cell.
o
The extra cells act as backup and the cells last longer.
Eg. If three 1.5V cells are connected in parallel, electrons receive 1.5V energy only.
o
This is similar to two waterfalls on rivers next to each other. Water only travels down one waterfall.
 Water Analogy:
If you pump twice as much water to the top of the building, you could turn the
wheel for twice as long however, all of the water will only have the gravitational potential energy from
being lifted just one level
Complete pg 394 (1-3)
25
Day 10
Lab Activity: Loads in Series
Purpose: To investigate the characteristics of electric circuits with loads in series.
Materials: 2 cells, 3 bulbs, 3 bulb holders (sockets), connecting wires, voltmeter and ammeter (or digital
multimeter)
Method:
1. Construct a circuit with two (2) cells in series and one (1) bulb.
2. Measure the electric potential across the cells and record the results in the "Electric Potential" table
below. (Remember, electric potential is measured across the device; the circuit does not need to be
disconnected in order to make a measurement with the voltmeter).
3. Measure the electric potential across the bulb and record the results in the table below.
4. Measure the current at the negative terminal of the battery and record the result in the "Current"
table below. (Remember, current is measured in the circuit; the circuit must be disconnected in
order to connect the ammeter).
5. Measure the current in the circuit "after" the bulb and record the result in the table below
6. Repeat steps 3 to 5 with two (2) bulbs in series and then again with three (3) bulbs in series.
Observations:
Electric Potential (V) Two cells connected in series:______V
# of bulbs
Across bulb #1
Across bulb #2
Across bulb #3
1
2
3
*hint for teacher: the sum of the electric potential across each row should be 3.0 V.
Current (A)
# of bulbs
After battery
After bulb #1
After bulb #2
After bulb #3
1
2
3
Questions:
1. Draw a separate schematic circuit diagram for each arrangement of bulbs in the activity and label
the electric potential and current readings at the appropriate connection points.
2. What happens to the brightness of the light from the bulbs as each bulb is added?
_______________________________________________________________
26
3. a) What happens when one of the bulbs is unscrewed? Explain why.
____________________________________________________________________________
b) How many paths for current flow are there in a series circuit? ________________
4. What conclusion can be made about the amount of current flowing in a series circuit?
_____________________________________________________________________
5. For each of the three series circuits, compare the electric potential of the cells to the electric
potential measured across the bulb(s). What general relationship seems to exist?
________________________________________________________________________________
Schematic Diagrams :
1.
2.
3.
27
Day 11
Lab Activity: Loads in Parallel
Purpose: To investigate the characteristics of electric circuits with loads in parallel.
Materials: 2 cells, 3 bulbs, 3 bulb holders (sockets), connecting wires, voltmeter and ammeter (or digital
multimeter)
Method:
1. Construct a circuit with two (2) cells in series and one (1) bulb.
2. Measure the electric potential across the cells and record the results in the "Electric Potential" table
below. (Remember, electric potential is measured across the device; the circuit does not need to be
disconnected in order to make a measurement with the voltmeter)
3. Measure the electric potential across the bulb and record the results in the table below.
4. Measure the current at the negative terminal of the battery and record the result in the "Current"
table below. (Remember, current is measured in the circuit; the circuit must be disconnected in
order to connect the ammeter)
5. Measure the current in the circuit "after" the bulb and record the result in the table below.
6. Repeat steps 3 to 5 with two (2) bulbs in parallel and then again with three (3) bulbs in parallel.
Observations:
Electric Potential (V) Two cells connected in series:_______V
# of bulbs
Across bulb #1
Across bulb #2
Across bulb #3
1
2
3
Current (A)
# of bulbs
After battery
After bulb #1
After bulb #2
After bulb #3
1
2
3
Questions:
1. Draw a separate schematic circuit diagram for each arrangement of bulbs in the activity and label
the electric potential and current readings at the appropriate connection points.
2. What happens to the brightness of the light from the bulbs as each bulb is added? ____________
3. What happens when one of the bulbs is unscrewed? _____________________________________
4. How does the electric potential measured across the dry cell compare to that measured across the
three bulbs? ________________________________________
5. Compare the amount of electric current flowing from the cells compared to the current flowing
through each of the three bulbs. _________________________________________________
6.
Suppose 15 light bulbs were connected in series, and one bulb burned out. How could
defective bulb be found? _______________________________________
the
28
7.
How could one defective bulb be identified if the 15 bulbs were connected in parallel? Explain.
______________________________________________________________________
8.
Are the electric wall outlets in homes wired in series or parallel? Explain.
______________________________________________________________________
Schematics :
1.
2.
3.
29
Investigation Parallel and Series Circuits (pg 360)
The Series Circuit:
current flows through a ____________path consisting of parts of the circuit which are wired to one another
Analogy (fig 11.1 pg 354)
Electrons push on the electrons ahead resulting in a smooth, even flow of current.The current at any one
point in a series circuit is exactly the same as the current as any other point in the circuit. A series circuit
can be compared with a race track. Cars are like electrons flowing around in a series circuit. All cars are
filled with gas at a pit stop and travel smoothly around the same closed path.
The Parallel Circuit:
current flows through ________________paths called __________ circuits Analogy (fig 11.2 pg 355)SP
In a parallel circuit, charges flow around two or more different loops. After leaving the power source, some
charges take one path, while other charges take the other. A parallel circuit is like city streets where Cars
have many paths to travel. One path might be a six lane freeway, while another is a two lane side street.
Like cars on a freeway compared to a side street, the current in a parallel circuit is not the same at
different points.
The fact that electrons in a series circuit flow around a single path and electrons in a parallel circuit flow
around in different paths (branches) brings us to the following Laws.
Current Law:
At any connection in an electric circuit, the current flowing into the connection is equal to the total current
flowing out of the connection.
Series: It = I1 = I2 = I3 Parallel: It = I1 + I2 +I3
Voltage Law:
The algebraic sum of the potential differences around any closed pathway or loop must equal zero.
Series: Vt = V1 + V2 + V3 Parallel: Vt = V1 = V2 = V3 .
Sketch schematics below for a series and parallel circuit . See page 354 and 355. Diagram A ; 3 1.5 cells in
series; Current from source = 1 amp ; 3 bulbs connected in series
Diagram B : 3 1.5 V cells in series ; current = 1amp ; 3 bulbs connected in parallel
Complete page 358 ( 1-4 )
30
Series Circuit
One path for the electricity to flow means that
charges making up the current flow from one load
to the next moving through all loads until coming
back to the source again.
Current (I in amperes A) at any point in the circuit
is the same as the current at any other point in the
circuit.
Parallel Circuit
Two or more paths for the electricity to flow means
that charges making up the current flow through
different paths and therefore do not move through all
loads before coming back to the source again.
1.5
A
1.5
A
+
+
Sum of Current in a Circuit
Series
Is = I1 = I2 = I3
Parallel
Is = I1 + I2 + I3
I3 1k
I2 1k
I2 1k
Is 1.5
I1 1k
I1 1k
Is 1.5
I3 1k
The current passing through each of the 3 resistors
and the current entering and leaving the source are
exactly the same.
The sum of the current passing through the 3
resistors is the same as the current entering and
leaving the source.
I. Use the Electricity Book web site to answer the next few questions
http://www.uce.ac.uk/education/research/cript/electricity%20book/frame%20start.htm
Start with the section Series and Parallel
Series – Explain what happens when the bulb breaks?
Paralle1 – Explain what happens when the bulb breaks?
Christmas Tree with bulbs in series – Why do newer Christmas tree lights use parallel circuits?
II. Use the Ohm Zone to answer these questions and complete listed activities.
http://www.article19.com/shockwave/oz.htm
Follow the hand and select Building a Simple Circuit first to see how the program works. Notice that this
web site shows the flow of current from the positive side to the negative side but our course (and Ministry
of Education) requires that we use the model with the flow from the negative terminal of the battery
(excess electrons) to the positive terminal of the battery (deficiency of electrons).
31
Click on the hand again and select Building a Series Circuit this time. In a series circuit, elements are
connected _____ after __________. This provides
______________________________________________. Follow the instructions to remove the bulb. If a
connection in a series circuit is broken, the current _________ through all other elements will
____________.
Click on the hand again and select Building a Parallel Circuit. A ________ circuit provides two or more
_______ for the current to follow. In the circuit, notice that the current flows from the battery to point A,
where it _____________________________. Try out the activity. At point B, the 2
____________________________________ into ___________ to return to the battery. If one of the
parallel connections is broken,
_____________________________________________________________________.
Click on the hand again and select Building Combination Circuit. Try out the activity and read this section.
Notice the combination circuits follow the principles of series circuits in the areas that have series
connections and follow the principles of parallel circuits in the areas that have parallel connections.
Click on the hand again and select Current in a Series Circuit. The current intensity in a ________ circuit is
the _________ through each circuit element. Try moving the ammeter around to see what the reading is
at each point in the circuit.
Click on the hand again and select Current in a Parallel Circuit. In parallel circuits, the current intensity will
be highest in the circuit element that has the lowest resistance (true because of Ohm’s Law). To find the
current (I) first find the resistance (R) by hovering over each element. Next, use the voltmeter to find the
potential difference (V). You can find the current now by using Ohm’s law (V=IR, I=V/R) or you can just
use the ammeter to check it. Add up the current reading at A, B, and C to get a reading of ____A. Now
place the ammeter after the battery and notice the reading is 1.15 A too! This means that Is=IA + IB + IC
for parallel circuits.
Complete CYU 11.1 2,4 using www.tina.com or paper and pencil to make drawings and find the current at
different points in the circuits.
III. For additional review and problems use the bite size website
http://www.bbc.co.uk/scotland/education/bitesize/standard/physics/electricity/series_and_parallel_circuits_
rev1.shtml
Review Parallel And Series Circuits and answer question 1.
Move to Current in a Series Circuit and try the activity.
Move to Current in a Parallel Circuit and try this activity. This is good review.
32
WORKING WITH CIRCUITS
1. Label the parts of Figure A with the following terms:
chemical (energy)
electrical (energy)
light and heat (energy)
source
conductor
load
______________ energy
Figure A
_____________ energy
_____________ energy
Figure B
2. What kind of circuit is this? __________________
3. How many paths do the
electrons have to follow? _______
4. How many loads does this circuit have? ______
5. Is the circuit complete or incomplete? _______________
6. Are the loads working? __________
7. If one bulb were to blow out, the other bulb would
_________________
8. Adding another bulb would make the other two give off
less light / the same amount of light? (circle one)
Figure C
9. What kind of circuit is this?
_____________
10. How many loads does this circuit
have? ________
11. How many paths do the electrons
have to follow? ______
12. Is the circuit complete or incomplete? __________________
13. Are the loads working? ______________
14. If one bulb were to go off, the other bulb would give off
less light_/ the same amount of light__
(circle one)
33
15. Adding another bulb would make each bulb give off
less light_/ the same amount of light__
(circle one)
16. Is this a good way to wire a home? ____________
Figure D
17. What kind of circuit is this?
_____________________
18. How many paths do the electrons
have to follow? ___________
19. How many loads does this
have? _________ Name them.
____________
___________
Continue referring to Figure D.
20. Is the circuit complete or incomplete? ________________
21. Are the loads working? ________________
22. Is your home wired this way?_____________
Figure E
Look at Figure E
23. What kind of circuit is this?
_______________________
24. How many paths do the electrons have to follow? _________
25. How many loads does this circuit have _________
Name them ________________ __________________
26. How many switches does this circuit have? ________
27. Which appliance is working?____________________
28. Which appliance is not working? ________________
29. Is your home wired this way? ___________
Look at Figure F
30. What kind of circuit is this? _________________________
31. How many paths do the electrons have to follow? ________
32. How many loads does this circuit have? __________
34
Name them ______________________________________
Figure F
33. How many switches does this circuit have? _________
34. Which loads are working? ___________________________
COMPLETE THE CHART (Place a check in the correct column)
Parallel
Circuit
1. only one path for the electricity
to follow.
2. more than one path for the
electricity to follow
3. loads work or shut off one at a
time
4. all loads are on or all loads are
off
5. appliances share the voltage
6. appliances do not share the
voltage
7. good way to wire a home
8. not a good way to wire homes
9. an extra bulb makes the others
less bright
10. an extra bulb does not change
the brightness of the others
Series
Circuit
35
Day 12
Electric Circuits with Multiple Loads
Series
Parallel
Electric Current
Constant
Electric Potential
Energy is shared by the loads. The
sum of the loads should equal the
source voltage.
It= I1= I2…
Vt= V1 +V2+…
Each pathway allows a certain
amount of current to flow. The
sum of each pathway is the total
current for the circuit.
Each pathway receives the same
energy. The potential difference for
each pathway is the same as the
source.
I1 + I2… =It
Vt= V1= V2…
Advantages of a series circuit:
1.
Less energy (voltage) is used.
2.
Simpler to set up.
3.
Less current= safer
Disadvantages of a series circuit:
1.
One load stops, all stop.
2.
One switch controls all loads.
Advantages of a parallel circuit:
1.
Loads are independent.
2.
Loads get maximum voltage.
Disadvantages of a parallel circuit:
1.
More current with each load- can be unsafe.
2.
Uses more energy.
36
Electricity Search
1.
2.
3.
4.
5.
6.
An electric current is a flow of (A).
The path the (A) take is called a (B).
Current only flows when the (B) is complete, or closed.
The most common device to open and close the (B) is a (C).
In a DC (B), a (D) is used to give extra potential energy to the (A) to flow through the (B) again.
This potential energy is also called a (E), and the "push" that the (D) gives the (A) is measured in
(F).
7. This potential is needed because the (G) in the (B) is converting the (H) energy into another form
of energy.
8. This other form of energy could be (I) energy if it produces motion, or (J) energy if it produces
heat.
connectors
amps
protons
kinetic
battery
load
cell
thermal
switch
volts
circuit
wire(s)
voltage
electrons
light bulb
electrical
static
Chemical
physical
A
B
C
D
E
F
G
H
I
J
Day 13 Electrical Resistance and Ohm’s Law (pgs. 337– 339)
Electrons move easily through a good conductor e.g _____________is a good conductor. Electrons
l________ very little energy when they collide with __________atoms as they move through. Thus, little
electrical energy is converted into ____________.
Tungsten, the filament in light bulbs, is a _________conductor. Electrons lose much more of their energy
when they collide with tungsten atoms. Thus, much electrical energy is converted into heat and light.
Tungsten’s resistance is ______________ x that of copper’s resistance
37
The ability of a substance to impede the flow of electrons is called ___________. Some electrical devices
used in circuits are designed for this purpose and are called __________. The symbol of electrical
When electrons flow through a conductor, the electrical resistance causes a _________ of electric potential
(voltage). This loss is referred to as electric potential difference, voltage drop, or the potential difference
across a conductor.
resistors- are designed to impede the flow of electrons
Symbol: R
SI Unit: Ohm (Ω)
Voltage Drop – depends on resistance and amount of current
V= IR
Ohm’s Law
Potential Difference (Voltage Drop) = Current x Resistance
Ohm’s Law only applies to “ohmic resistors”. They are not affected by temperature changes.
FACTORS THAT AFFECT RESISTANCE (342)
a.
TEMPERATURE
-higher temperature, _________resistance (harder for electrons to flow through disorganized, fast moving
electrons)
b.
LENGTH
- ____________ resistance with wire length (resistance __________as length doubles...harder to flow
greater distance relative to shorter distance)
c.
CROSS SECTIONAL AREA
- ____________ resistance with larger area (more area for electrons to flow...easier)
d.
MATERIAL
-structure of atoms may allow electrons to move better or worse, depending on how well atom holds onto
electrons
38
Day 14 Resistance
Voltage or Potential = Current
Difference
(Amperes)
(Volts)
x Resistance
(Ohms)
V=IxR
I =V/R
R=V/I
Questions
1. In what units are the following measured: (a) voltage or potential difference (b) current (c) resistance?
2. State how voltage and current are measured.
Potential Difference
(Volts)
12
9
6
3
Current
(Amps)
4
3
2
1
Resistance
(Ohms)
Current
(amps)
Potential Difference (volts)
3. On the axes above, graph the above data with potential difference on the X-axis and current on the Yaxis. (a) What do you notice about the graph? (b) Using the resistance rule, calculate the resistances in
the table. What do you notice?
4. What voltage or potential difference is used by an electrical appliance that draws 0.4 amps of current
and has a resistance of 3 ohms?
5. A light bulb uses 240 volts of electricity and draws a current of 2 amps. What is its resistance?
6. Calculate the current used by a television that runs on 240 volts and has a resistance of 600 ohms.
7. Three light bulbs each drawing 240 volts and 0.3 amps are connected in series. What is the resistance
of each light bulb and what is the total resistance?
8. Complete the following table:
(a)
(b)
©
(d)
(e)
Answers
Current
(amps)
Resistance
(ohms)
0.1
0.25
0.4
0.5
600
1000
1000
Voltage
(volts)
240
240
200
1. (a) straight line graph (b) R = 3 ohms 2.(a) volt (b) amp (c) ohm 3. Voltage measured by voltmeter
wired in parallel; Current measured by ammeter wired in series 4. 1.2volts 5. 120 ohms 6.0.4 ohms 7.
800 ohms ; Add them if they are in series to get 2400 ohms 8. (a) 60 volts (b) 250 volts (c)600 ohms (d)
480 ohms (e) 0.5 amps
39
Resistance Calculations Worksheet
resistance = potential difference
current
Units: R is Ω (ohms)
V is V (volts)
I is A (amperes)
R=V
I
1. Find the unknown quantity:
a) I = 10 A
R = 1500 Ω
V=?
b) I = ?
R = 200 Ω
V = 240 V
c) I = 15 A
R=?
V = 110 V
2. Find the unknown quantity (CONVERT FIRST to the unit with no prefix)
a) I = ?
R = 2000 Ω
V = 20 mV = ________ V
b) I = 25 mA = _________ A
R=?
V = 110 V
c) I = 1 kA = ________ A
R=?
V = 50 mV = ________ V
WORD PROBLEMS
1. How much resistance does a light bulb create if it has a current of 25 mA around it in a 9 V circuit?
2. A heating coil offers a resistance of 2.5 kΩ. What voltage is required so that 1.5 A of current pass
through it?
3. The human body offers a very small amount of resistance (let’s say 1 mΩ for argument). If a lightning
bolt (said to have 1.21 GV of potential according to a famous movie called Back to the Future released in
1984), hits you how much current is flowing through your body.
Complete page 342 ( 1-6 )
40
SNC 1D
Grade Nine Science
Current Electricity Review
Complete this sheet after a review of your notes and chapter 10 of your text book.
1. A coulomb is __________________ electrons and is also a measure of ________________. The
symbol for this quantity is ________.
2. An Ampere measures ____________________ and is equal to one ________________ per second.
The symbol for this quantity is _____________.
3. Knowing the relationship current = charge moving past a point/time…predict which current will be
greater, the current passing through an electric razor or the current passing through an electric iron,
when each is plugged into a 120 V home outlet. (hint refer to table 10.2 on page 325)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
4. What relationship do you notice between the type of appliance and the amount of current they require
(refer to table 10.2) Consider the type of energy produced by the high current devices.
_________________________________________________________________________________
_________________________________________________________________________________
5. A volt is a measure of ______________________________________ and can be determined by
dividing the _______________ by the _______________ for a circuit. A volt is equal to one Joule per
____________
6. The relationship between potential difference (volts) and current (amps) is given by ohm’s law. An
ohm is a unit of _______________ and the symbol is the Greek letter ____________. In
mathematical form, Ohm’s law can be stated….
Resistance = ---------------------7. Carefully read page 337 on resistance and explain why the filament of light bulbs is made up of
tungsten rather than copper.
__________________________________________________________________________________
__________________________________________________________________________________
8. Carefully review the model problem on page 338. This problem illustrates the relationship between
resistance, current and electric potential for a typical electric heater connected to a 120 V home outlet.
Use this information, and sample problem to determine the different resistances of a colour TV and an
electric kettle connected to a 120 V home outlet. (hint, remember the current needed for these
devices is listed in table 10.2 on page 325) Use the back of this sheet to solve this problem.
41
Day 15 Resistance in Series and Parallel Worksheet(356-358)
Resistors in series
Resistors in parallel
Requivalent = R1 + R2+ R3 =
1
1
Requivalent = R1
+ 1 + 1 =
R2
R3
1. Find the equivalent resistance of these series circuits (in Ω) :
a) R1 = 100 Ω
R2 = 20 Ω
R3 = 55 Ω
b) R1 = 7500 Ω
R2 = 1.5 kΩ
R3 = 25 Ω
c) R1 = 0.1 Ω
R2 = 0.2 Ω
R3 = 50 mΩ
2. Find the equivalent resistance of these parallel circuits (in Ω) :
a) R1 = 100 Ω
R2 = 20 Ω
R3 = 55 Ω
b) R1 = 7500 Ω
R2 = 1.5 kΩ
R3 = 25 Ω
3. Calculate the equivalent resistance of the following circuits:
a) R1 = 5 Ω R2 = 10 Ω
b) R1 = R2 = R3 = 1.5 Ω
c) R1 = 0.1 Ω
R2 = 0.2 Ω
R3 = 50 mΩ
42
c) R1 = 12 Ω R2 = 5 Ω R3 = 8 Ω
4. Three light bulbs of 4 Ω resistance each are in a parallel with a 9V power supply. Draw the circuit, and
find the current.
Day 16 POWER (343)
-the amount of energy that can be converted into heat, light, sound, etc. per second
Power (units = W...watts) = Energy (J) / Time (s)
P = E/t
Also, P = VI
Power Calculations Worksheet
power = energy
time
P=E
t
1. Find the unknown quantity:
a) E = 10 J
P = 100 W
t=?
b) E = ?
P = 75 W
t = 20 s
Units: P is W (watts)
E is J (joules)
t is s (seconds)
c) E = 15 kJ
P=?
t = 20 s
43
2. Find the unknown quantity (CONVERT FIRST to the unit with no prefix)
a) E = 1.2 kJ = ________ J
P = 75 W
t=?
b) E = 55 J
P=?
t = 2.25 hrs = _________ s
c) E ?
P = 200 MW = ________W
t = 0.5 hrs = __________s
WORD PROBLEMS
1. How much energy passes through your bedroom lamp (containing a 100 W light-bulb) every evening
when you read for half an hour before you going to bed at 9:45pm?
2. 100 MJ of energy passes through a generating station every minute. What is its power rating?
3. How long will a 75 W bulb glow for on 1 kJ of energy?
Questions
1. A gasoline-powered generator consumes 15 000 J of energy in 5.0 minutes. How much power did it
produce in this time?
Calculations:
2. A toaster connected to a 110 V power source has 6.0 A of current flowing through it. How much power
is dissipated as heat?
Calculations:
3. A light bulb draws 1.25 A of current from a 120 V gasoline-powered generator.
(a) How much power does the generator produce?
Calculations:
(b) If the generator runs for 5.0 minutes, how much energy will the lamp convert into heat and light?
Calculations:
44
Day 17 Science, Gr. 9
Characteristics of Electricity – Measuring Electricity
Mixed Electricity Problems
DON’T FORGET TO CHANGE TO THE UNIT WITH NO PREFIX FIRST!
ALL OF THESE NEED TWO DIFFERENT FORMULAS
1. How many coulombs of charge pass through a 95 W amplifier plugged into a 110 V wall socket over the
course of a 2 hour concert.
2. A bulb plugged into a 110 V wall socket has a resistance of 100 Ω. Find how many seconds it takes to
pass 2000 C of charge.
3. 2500 coulombs of charge is passed over a 2 hour period across a certain capacitor. What is the
resistance of this capacitor if the voltage across it is 200 mV.
4. What is the power of a microchip that passes 1 C of charge with a potential difference of 0.01 mV in 1
second.
5. A simple circuit has a 9V battery attached to it. How long does it take to pass 1C of charge through
that battery if its resistance is 150 Ω.
6. What is the current in an electric stove element that creates 150 J of heat at 240 V over a 5 minute
period.
45
Day 18
Measuring Electrical Energy
Energy ~ the ability to do work
Electrical Energy ~ The energy transferred to an electrical load by moving electric charges
 Symbol E
 the SI unit for measuring energy is the joule ( enough energy to light a 100 W
light bulb for a one hundredth of a second)


Because the joule is so small, energy is also measured in larger units such as
the watt hour and the kilowatt hour.
The watt hour is 3600 times larger than the joule
Three Factors Determine the Amount of Electrical Energy
1. Voltage Drop ~ a measure of the energy each electric charge gave up as it moved through the circuit
2. Electric Current ~ A measure of the rate at which a the electric charges flowed out of the battery
3. Time ~ the time that the electric charges were flowing in the circuit while the light bulb was glowing.
Calculating the Amount of Electrical Energy
If you connect a battery to any type of electrical load until it is discharged, multiply the voltage drop,
current and time, you always get the same number. Scientists express this relationship in the form of a
formula:
Electrical Energy = Voltage Drop x Electric Current x Time Interval
E
= V x
I x t
Where E is the electrical energy measured in joules (J)
and
V is the voltage drop measured in volts (V)
I is the electric current measured in Amperes ( I)
t is the time interval measured in seconds (s)
Rated Capacity = Electric Current x Time Interval
ENERGY SYSTEM
-a device that converts one form of energy into another
eg. electric kettle converts electrical energy into sound and thermal energy
FIRST LAW OF THERMODYNAMICS -"energy is not created or destroyed, it just changes forms"
INPUT ENERGY = WASTE ENERGY + USEFUL OUTPUT ENERGY
input energy = amount of energy used to operate a system
output energy = amount of useful energy obtained from a system
waste energy =energy that is not useful (often thermal)
unit of energy = Joule (J) = 1000 J = 1 kJ (kilojoule)
EFFICIENCY =[ENERGY OUTPUT / ENERGY INPUT] X 100
eg. 500 kJ energy goes to electric kettle, which uses 490 kJ to heat water,and loses 10 kJ as heat and
sound
kettle efficiency = E out/ E in X 100 = 490 kJ / 500 kJ = 98 % efficiency
waste = 100 % - 98% = 2 % energy wasted
46
Efficiency Calculations ( pg 348 )
Questions
1. A clothes dryer has a power rating of 4356 W. It takes an average of 45 minutes to dry a load of
clothes. If the dryer used 8820 kJ of energy during this time, how efficient is this dryer?
Calculations:
2. Reading for an hour followed by an hour of homework, a student decides to check the efficiency of the
halogen desk lamp used. The lamp is rated at 20 W and used 20.88 kJ of energy, how efficient is it?
Calculations:
3. In conducting a science inquiry into how efficient a kettle design is, a student discovers that in 264
seconds 26°C water increases in temperature by 70°C for kettle “a” and 65°C for kettle “b.” The energy
transferred to 1 Kg of water in kettle “a” is therefore 292 600 J, and 271 700 J for kettle “b.” Each
design is a 1500 W kettle, what percentage of efficiency is kettle “a” and “b?”
Calculations:
4. Based on your answer to question 3, how much money does it cost to run each kettle for a 30-day
month? For what reason, therefore, would you choose between the kettles? Assume that the kettles
operate 30 minutes daily, and that electricity costs 10¢ per kilowatt hour.
Calculations:
47
Calculating Electric Power
Electrical power is a measure of the rate at which electrical energy is being used.
The SI unit is the watt and the symbol is W.
Electrical Power (E) = Electrical Energy (J) = Watts
Time Interval (s)
Formulae
P=
E=
E
t
P x t
t =
E
P
Answer in:
Watts
Joules
E
t
P
seconds
This formula is not often used because you have to measure both the energy and the time interval to be
able to solve the problem.
Although the joule (J) is the normal unit for energy, the large amounts of energy used in a home would
require the use of very large numbers. In the electrical meter, the energy is measured in kilowatt hours
(kW.h). Power is measured in kW and time is measured in hours (h). There are 3 600 J in one W.h or 3
600 000 J in one kW.h.,
Power can also be calculated using the voltage and current:
Electrical Power = Voltage Drop x Electric current
Formulae
P= VxI
V=
P
I
Answer in:
Watts
I =P
V
P
Volts
Amps
V
I
To find the cost of the electricity, multiple the rate charged by the electric company by the energy used.
Examples:
1. Calculate the power of a toaster that uses 72000J of energy in 50 s (time).
2. Calculate the power of a vacuum cleaner if the operating voltage is 120 V, and the current (I) flowing
through it is 7.90 A.
48
3. How many kilowatt hours (kW.h) of electrical Energy are used in four weeks by a clothes dryer that
has a power rating of 5 kW (P) and is operated for 4.5 hours (time) each week?
4. Calculate the cost of the electricity required to operate a freezer ( 500 W) for one month if it uses 75
kWh of energy (E). The rate charged for the electricity is $ 0.08/ kWh.
ELECTRICAL POWER PROBLEMS
1. Calculate the power rating of an electric toaster that uses 210 000 J of Energy while toasting bread for
140 s (time).
2. Calculate the power rating of a coffee grinder that operates on a voltage of 120V. A current of 1.7 A
flows in the motor.
3. Calculate the Energy used by a coffee maker that has a Power rating of 0.900 kW and
for a time of 17 h.
operates
4. How much Energy is used by a 1.5 kW (P) electric kettle that operates for a time of 0.80 h per day
for two weeks.
5. What is the current (I) drawn by a 100 W light bulb operating at a voltage drop of 120 V?
6. What is the voltage drop across a 1248 W baseboard heater that draws 5.20 A ?
49
7. What is the maximum power that may be used in a circuit with a voltage drop of 120 V
and a 20 A fuse?
8. Calculate the cost of operating a 3.6 kW oven for 3.0 h, at a rate of $0.08/kW·h.
9. Calculate the cost of operating a 400 W spotlight for 2.0 h a day for 30 days , at a rate of
$0.08/kW·h.
10.
What is the cost to a store owner of leaving a 40 W light burning near his safe over the
weekend, for 60 h, if electricity costs $0.08/kW·h?
11.
The blower motor on an oil furnace, rated at 250 W, comes on for an average of 5.0 min
at a time, a total of 48 times a day. What is the monthly (30 day) cost of operating the
motor, if electricity costs $0.08/kW·h?
12.
A 300 W refrigerator compressor operates for an average of 6 h per day. Calculate the
annual cost of operating the refrigerator, if electricity costs $0.08/kW·h.
Ans.
1) 1500 W 2) 204 W 3) 15.3 kW·h 4) 16.8 kW·h 5) 0.833 A 6) 240 V
7) 2400 W 8) $0.86 9) $1.92 10) $0.19 11) $2.40 12) $52.56
Pg 348 (1-5)
50
Day 19 Electrical Energy Use in the Home (368)
What unit is used to measure the amount of energy your house uses? ________________
Look at the meter on page 368 :
October 28 # of kilowatt hours (kW.h) = ____________________
August 30 # of kilowatt hours (kW.h) = ___________________
Subtract the 2 values = _____________________ = amount of kW.h used
If the cost = 8.0 cents per kW.h .
Calculate the total cost = total energy used kW.h x cost in $/kw.h
___________ x ___________= ____________________
The Price of Energy
Questions
1. A meter reader determines that a business has used 3550 kW•h of energy in two months. If electricity
costs
10 cents per kW•h, calculate the bill.
Calculations:
2. An electric heater draws 1100 W of power. Electricity costs eight cents per kW•h. How much does it
cost to operate the heater 3 h a day for 30 days?
Calculations:
3. A 750 W toaster and a 1200 W electric frying pan are plugged into the same 100 V outlet. How much
will it cost to operate the two appliances at eight cents per kW•h?
Calculations:
4. A toaster is used an average of 5 h per month. The toaster draws 8 A of current from a 110 V outlet. If
electricity costs eight cents per kW•h, how much will it cost to operate the toaster for one year?
Calculations:
Pg 350 (1-6),8,11,13,14,17,20,21,22,23,24,25,26,27,28
Pg 378 (1-7),8,10,11,17,21,22
51
Independent research
produce a plan of action to reduce electrical energy consumption at home (e.g., using EnerGuide
information when purchasing appliances), and outline the roles and responsibilities of various groups (e.g.,
government, business, family members) in this endeavour [IP, AI, C]
Issue: Replacing incandescent light bulbs with compact fluorescent bulbs can reduce the energy needed to
light a home by 75%. Although the bulbs are more expensive than incandescent bulbs, electrical companies
sometimes provide coupons to reduce the price. Also, the Ontario government is phasing out incandescent
bulbs, which will further reduce energy consumption.
Questions:
What are EnerGuide and ENERGY STAR, and how can they be used when purchasing appliances or
electronics?
What is the difference in energy consumption between a conventional and a front-loading washing
machine?
What appliances consume electrical energy even when they are not in use?
52
Which Light Bulb Is Best?
Light bulbs are used for many different purposes in a home. In your own room, you likely have a desk
lamp, a ceiling light, and maybe a bedside lamp. Bulbs used to come in standard wattages of 40, 60, and
100 W. Now, different energy-efficient types of bulbs are available.
How much longer do these new bulbs last? Are they cost-efficient as well?
1. How many kilowatt-hours does a 60-W incandescent bulb use during a 12-hour period?
__________________________________________________________________________________
__________________________________________________________________________________
2. How many kilowatt-hours does a 15-W compact fluorescent bulb use during the same period? (Both
bulbs provide the same light intensity of 900 lumens.)
__________________________________________________________________________________
__________________________________________________________________________________
3.If the utility rate is $0.10 per kW•h, how much does it cost to run each light bulb in questions 1 and 2?
__________________________________________________________________________________
__________________________________________________________________________________
4. According to the information on their packages, the compact fluorescent bulb lasts 10 000 hours and
the incandescent bulb lasts 1350 hours. How much money will you save in electricity charges over the
life of each bulb?
__________________________________________________________________________________
__________________________________________________________________________________
5. If the compact fluorescent bulb costs $30.00 to buy and the incandescent bulb costs $2.00 to buy,
which bulb is more economical over the long term? (Hint: To make this comparison, assume 10 000
hours of operation. This will require purchasing more than one incandescent bulb, so you will need to
determine how many.)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
53
Day 20
Power Generation Reading Assignment (pages in SciencePower9)
1. Systems at a Glance
Visit http://www.opg.com/power/ to learn about power generation in Ontario.
As of December 31, 2006 OPG’s electricity-generating portfolio had a total in-service
capacity of 22,000 megawatts (MW)*.
This consisted of:
operating nuclear units with a capacity of ______________TWh
http://www.opg.com
fossil-fueled stations with a capacity of ______________TWh
hydroelectric power with a capacity of ____________TWh
29 EcoLogoM-certified green power hydroelectric stations with a capacity of 12MWh
Green power stations with a capacity of _____________MW
List 1 example of a green power station including the location. _____________________________
Hint: check out the map and the other links on nuclear, fossil, hydro.
Hydroelectric Power
2. From p395 of SciencePower 9
Most of Canada’s electricity comes from _________ power.
Energy from Flowing River
 Uses water (_________) pressure to generate electrical energy
 Large ____ cause the water levels to rise above the power plant
 As the level rises the _________ underneath the water ___________
 Water pressure at the bottom of the dam is therefore enormous
 A channel (called a _____________) directs the water from the bottom of the reservoir to a _________
 High pressure of the rapidly flowing water turns the turbines and the turbines turn the generators
 Generators convert ________ energy (energy from the motion of the turning turbine) into electrical
energy
 High voltage power lines carry the electric energy over many
kilometres from the plant to communities
http://www.ec.gc.ca/water/en/manage/use/e_hydro.htm
54
3. Visit http://www.opg.com/power/hydro/howitworks.asp for a diagram of hydroelectric power
generation. Fill in the blanks about generator portion.
In very simple terms, electricity is produced by _________ _______-magnets inside a coil of wire in a
__________ to create a ______ of ___________. To keep the electro-magnets spinning, a hydroelectric
station uses falling water.
Advantages
Disadvantages
http://www.tva.gov/power/hydroart.htm
Fossil Fuels
4. How fossil fuel works (coal fired power plant)
http://www.tva.gov/power/coalart.htm
Electricity is produced at a coal-fired fossil plant by the process of _________ water in a boiler to produce
________. The steam, under tremendous _________, flows into a __________, which spins a
____________ to produce electricity.
Fossil Fuel Power (Coal-fire Generation)
Advantages
http://www.tva.gov/power/coalart.htm
Disadvantages
55
Nuclear Power (CANDU Reactor Generation)
Advantages
Draw Fig 12. 12 and label
Wastes)
Disadvantages
p. 403 (Nuclear Energy Leaves Radioactive
56
Tidal Energy
Advantages
Draw Fig 12. 27 and label
Disadvantages
p. 412 (Tidal Energy)
List the sources of electricity in Canada according to their importance: (p. 398)
Examples of this source
Most
1.
2.
3.
4.
Least
5. Internal Combustion
gasoline powered generators
Define the following terms: (p. 407)
RENEWABLE ENERGY SOURCE –
NON-RENEWABLE ENERGY SOURCE –
Classify the following sources of energy: (various pp. 394 – 413)
solar-cell
nuclear gasoline-generator
hydroelectric dam
tidal
wind
solar collector gas-fire wind
renewable
non-renewable
57
Answer the following questions:
1. The one component that is common to almost all forms of power generation is the turbine.
a. What is a turbine? (p. 395)
b. How is the turbine used to create electricity? (p. 395)
2. Complete the table:
(pp. 395, 396, 397, 398, 411, 412)
Form of Power
What is the original source of the energy?
What substance turns the
turbines?
hydroelectric
(dam)
coal-fire
heat from burning coal
steam
nuclear
wind
tidal
diesel, gas, and
internal
combustion
(p. 398 Canada’s
Energy
Resources)
pg. 416 (6,7)
water
58
-
watch video www.teachersdomain.org : energy sources and answer questions below :
-renewable.
watch video www.teachersdomain.org : alternative energy
Independent Research
assess some of the social, economic, and environmental implications of the production of electrical energy
in Canada from renewable and non_renewable sources (e.g., wind, solar, hydro, coal, oil, natural gas,
nuclear)
Issue: The operation of wind farms along Lake Huron produces electricity from a renewable source,
reducing dependence on non-renewable sources of electricity. However, the wind farms produce noise and
visual pollution, affect local animal life, and reduce the amount of land available for agriculture.
Questions:
What is the price difference between electricity produced from solar power and by coal-burning plants?
What effects do coal mining, oil production, wind farms, and hydroelectric dams have on surrounding
ecosystems?
59
What types of hazardous substances are used or created in the production of solar power and nuclear
power?
What types of emissions are produced by coal-burning and hydroelectric power plants?
What are the effects of these emissions on human health and the environment?
Test Review 422 (1-30)34, 36,38,39,40,41,42
60
Unit 3 Review
1. What is the difference between an insulator and a conductor? Give two examples of each.
2. By adding positive and negative charges, make the first circle positively charge, the second negatively,
and third neutral. After you have drawn them determine the overall charge.
Overall:
Overall:
Overall:
1. Complete the charges on this diagram of lightning just before it strikes.
ground
2. What is the purpose of a lightning rod?
3. Explain clearly why a balloon rubbed with fabric will produce static electricity but a metal bar rubbed
with fabric will not. Include the words charges moving freely, charges building up in one place,
insulator, conductor in your explanation.
4. Add positive and negative charges on the following pair of objects. Make sure there is a difference
between the charges on each object. Add a spark in the correct direction.
5. Draw the four diagrams that were used to explain induction. Add descriptions in your own words to
make it clearer.
61
Electricity Problems
1. If there is a current of 15 amperes in a circuit for 5 minutes, what quantity of electric charge flows
through the circuit?
2. 1 MW of power is produced by the Bearskin Lake generating station every Christmas day. How much
energy is consumed between 9:00am and 5:00pm on December 25 th?
3. 1.2 x 103C of charge passed through a transformer over a 5 minute period. What is the resistance of
the transformer if its potential difference is 240 V.
4. A buzzer plugged into a 110V wall socket has a resistance of 1.25 x 10 2 Ω. Find how many seconds it
takes to pass 1C of charge.
5. Draw a circuit that has a bulb attached in series to a 1.5 V cell, an ammeter and a switch. Find the
resistance of the bulb if the switch is closed and the ammeter reads 1.2x10 -2 A.
6. What is the equivalent resistance of four resistors (3 Ω, 6 Ω, 9 Ω, and 12 Ω) when:
(a) they are attached in series?
(b) they are attached in parallel.
7. Three 25 Ω resistors are attached in parallel. There is a cell and an ammeter.
(a) Draw the circuit.
(b) If the cell offers 6 V of potential difference what is the current on the ammeter?
62
63
D. Power Generation
1. State how the following are important in power generation:
(a) turbine
(b) generator
2. List three renewable and three non-renewable forms of power generation.
Renewable
1.
2.
3.
Non-renewable
1.
2.
3.
3. What are the major disadvantages of the following forms of power generation:
(a) coal
(b) nuclear
(c) hydroelectric dam