Electricity!! What comes to your mind when you read about
this word? Do you think about your video game? A lightning
lightning storm?
The lights of your city in the night?
You use electricity when you turn on the lights. You also use
use it
when the lights go out and you turn on a flashlight.
You use electricity when you listen to the radio in your room.
You carry it with you when you take along your portable DVD
player and listen to it through your headphones.
Electricity is a form of energy you use everyday, from the
time your alarm wakes you up until the time you turn off your lights
before going to sleep. Electricity supplies energy. You can’t see it,
but you can see what it does.
1
Just the Facts
• If two objects push each other away, then they have the same type of
charge.
• If two objects pull toward each other, then they have different types of
charges.
• They tiny part of an atom has a negative charge, it is called an electron.
• If an object loses some of its electrons, it will have a positive charge.
• If you have an object that has a negative charge, when you rub it, it will
lose its charge.
• If a balloon with a charge is held next to a balloon without a charge, the
balloons will pull toward each other.
• When a balloon with a negative charge is brought near a piece of wool with
a positive charge, the balloon will be pulled toward the wool.
Red Balloon with charge
Green Balloon without a charge
Green balloon pulling toward red balloon
Orange Balloon with negative charge
Wool with a positive charge
Orange balloon is being pulled toward the wool.
2
Electricity Lesson 1
You Will Get A Charge Out of This!!!!!
As mentioned previously, electricity is invisible. You
can’t see it or hear it, but you can feel the effects of electricity.
Do you hear your clothes crackle and see them cling together
when they come out of the dryer? Do you feel the shock you get
after you walk across a carpet and touch something or
someone? These events are caused by electricity. Electricity
supplies energy.
All matter and all living things are made up of
atoms. An atom is
very, very tiny pieces called atoms
made up of smaller particles called protons,
electrons,
neutrons. These particles have a
elec
trons, and neutron
property called a charge
charge. All electricity is caused
by charges. Some have a positive charge (protons
protons);
protons
others have a negative charge (electrons
electrons).
electrons Most of
the time, the number of charges is equal (neutrons
neutrons).
neutrons That means
they balance each other.
When two objects are rubbed together, some of the
negative charges (electrons) move from one object to another.
The number of positive and negative charges is no longer equal
or balance. The charges are unbalanced.
You unbalance charges when you rub a balloon with a piece
of wool. Some of the negative charges (electrons) move from
the wool to the balloon. The charges on the balloon are no longer
balanced. The balloon now has more negative charges. The
negative charges (electrons) do not move. They are called static
charges. Static means “not moving.” Static electricity is
3
electricity produced with static charges. The pictures below
show this phenomenon.
+ - +
- + + + -
++--+
++-
+
-++
+-
Charges balanced
+- +
--- +++- -
Charges unbalanced
Unlike charges attract each other, like charges repel (or
move away) from each other. When you rub a balloon on your
hair or a piece of cloth, you give it more of one type
of charge. That’s why the balloon sticks to the wall.
The positive charges on the wall attract the negative
charges on the balloon. When you rub a balloon with your
hands, the extra charge moves to your body, spreads out,
and travels to the ground. Getting rid of extra electrical
charges by safely transferring it to the ground is called
grounding. Grounding is the easiest way to get rid of static
electricity.
The small amounts of static electricity we experience can
cause an annoying shock. Large amounts of static electricity
can cause lightning and can be very dangerous. Static
electricity builds up in the clouds when the atoms bump together
and rub against each other. When the electricity travels to the
ground you see lightning. Lighting rods are put on the roofs of
buildings to carry the electricity away from the building. It works
because part of the lightning rod is connected to the ground with
a wire (grounding).
4
+-+-+-++-+-+-+
+-+-
-+-+
+-+_
+-+_
Static Electricity
Have you ever rubbed a balloon on your hair and then stuck the
balloon to the wall? Static electricity was at work!
All matter is made up of tiny particles called atoms. Each
atom contains 3 basic parts:
protons which have a positive electrical charge (+),
electrons which have a negative electrical charge (-),
neutrons which have no electrical charge.
Protons and neutrons are in the nucleus or central core of
an atom, while the electrons orbit around the nucleus. Most objects, such as a
balloon, normally have about the same number of electrons and protons, making
them electrically balanced.
Sometimes objects gain or lose electrons through friction (rubbing 2 things
together). When this happens, the object becomes electrically charged. If an
object gains electrons when it is rubbed, it becomes negatively charged because it
has more electrons (-) than protons (+). If an object loses electrons when it is
rubbed, it becomes positively charged because it has more protons (+) than
electrons (-).
When a balloon is rubbed on your hair, it gains electrons from your hair and
becomes negatively charged. Your hair becomes positively charged and will stick up
because like charges repel (or pull away). When the negatively charged balloon is
brought near your hair, it will be attracted because unlike charges
attract.
Like Charges (repel)
Unlike Charges (attract)
When the negatively charged balloon is brought near a wall, it
induces a positive charge near the surface of the wall (the extra
electrons on the balloon repel electrons near the surface of the
wall). Since opposite charges attract, the balloon sticks to the wall.
5
Atoms and Electricity
Electricity is the energy in charged atoms. The mystery of electricity will be
easier to understand if you study the parts of an atom. Atoms contain protons,
electrons, and neutrons. Protons and neutrons are clustered in the nucleus at the
center of the atom. Electrons travel around in the space outside the nucleus.
A proton has a positive (+) electric charge and an electron has a negative (-)
electric charge. A neutron does not have any charge.
Usually an atom has an equal number of
protons and electrons. In that case, the
positive and negative charges balance
each other and the atom is neutral (not
charged).
The diagram at the right shows a neutral
atom. Use the boldfaced words above to
label the four parts of the atom.
Sometimes an electron goes flying off of one atom and joins another atom. The
atom that gains an electron then has a negative charge since it has more electrons
(-) than protons (+). The atom that loses the electron then has a positive charge
since it has more protons (+) than electrons (-).
Study each atom diagram below. Write neutral if its charges are balanced. If not,
identify its charge as positive or negative.
Challenge! Draw two neutral atoms, each with four protons, four electrons, and four
neutrons. Then show how the same atoms would look if an electron left one atom and
moved to the other atom. Use the correct symbols like the diagrams above.
6
7
Models can help us understand how things behave. How do objects become
electrically charged? Read the data below. Then, complete the steps to the
experiment to find out how an object becomes electrically charged. Make sure to
read each step and follow all the directions given.
Objects with no charge contain an equal number of protons (+) and electrons (-).
Certain objects can gain or lose electrons when they rub against other objects.
When an object with no charge gains electrons, it has more electrons than protons.
It is said to be negatively charged. When an object with no charge loses electrons,
it has more protons (+) than electrons. It is said to be positively charged.
An unchanged balloon containing an equal number
of electrons & protons is shown here. Electrons are
represented by what symbol? ___________ The
protons are represented by what symbol? _________
Rub you neutrally charged balloon against a piece of wool.
Is you balloon going to gain more electrons or protons
from the wool? ______________
Draw how the charges on the balloon and the wool
change after they are rubbed together.
Once the negatively charged balloon is placed
against the wall, it repels the negative charges
in the wall. As the negative charges in the wall
move away from the wall’s surface, the wall’s
surface becomes positively charged. So the
balloon & the wall’s surface attract each & the
balloon sticks to the wall. Draw what the charges
look like when the negatively charged balloon is
stuck to the wall.
8
-+-++-+-+-+
-+-+-+
+-+-+-_
Many years ago, when sailing ships traveled at
night, sailors were sometimes frightened by a strange,
bluish light dancing on the mast of their ships.
The light was often accompanied by crackling noises.
They name the effect St. Elmo’s Fire after the patron saint
of sailors.
In the years since, St. Elmo’s Fire has become the
unwanted companion of aviators as well. Airplane pilots
sometimes see St. Elmo’s Fire when they fly near
thunderstorms or cumulonimbus clouds. The light appears on the wings and
propellers of airplanes, ships’ masts, and other objects that are higher than their
surroundings.
St. Elmo’s Fire, or corona discharge, is not a fire at all. It is really a
discharge of static electricity. Static electricity is called that to distinguish it from
current electricity; static electricity remains stationary until it builds up enough
electric potential to discharge, while the more familiar current electricity moves
through electrical circuits in a steady predictable manner. Static electricity often
builds up on tall objects when the atmosphere is full of electrical charges. That is
why St. Elmo’s Fire is most often seen and heard before or during a thunderstorm.
Static electricity can produce shock, St. Elmo’s Fire, lightning, and other
serious problems. In 1037, static electricity may have sparked the explosion of the
hydrogen filled airship Hindenburg as it was docking at Lakehurst, New Jersey.
Length
Diameter
Gas
Volume
Engines
Maximum
Speed
Lifting Gas
804 feet / 245.06 meters
135 feet / 41.15 meters
7,063,000 cu. feet / 211,890 cu.
meters
Four 1200 hp Mercedes Benz
engines
84.4 mph / 135 km/h
Hydrogen
9
Have you ever scuffed your feet as you walked across the carpet and then
brought your finger close to someone or something? Zap! Did the person jump?
The spark you made was static electricity. Static electricity is made when objects
gain or lose tiny bits of electricity called electrical charges. The charges are either
positive or negative.
Objects that have electrical charges act like magnets, attracting or repelling
each other. If two objects have like charges ( the same kind of charges, they will
repel each other. If two objects have unlike charges (charges that are different
from each other), they will attract each other.
Test you knowledge about static electricity by unscrambling the words in each
sentence below.
1. Flashes of (ghtlining) _________________ in the sky are caused by static
electricity in the clouds.
2. Electrical charges are either (ospivite)________________ or
(givanatee) _______________.
3. Small units of electricity are called (srgache) ______________.
4. Two objects with unlike charges will (arcttat) _______________ each other.
5. Sometimes electric charges jump between objects with (unlike) __________
charges. This is what happens when lightning flashes in the sky.
Look at the pictures below to see how static electricity affects objects.
1. Name the two objects that are interacting with each other.
2. Tell whether the objects have like charges or unlike charges.
Objects: _____________
Objects: ___________
Objects: _____________
Charges: ____________
Charges: ___________
Charges: _____________
10
Objective:
Objective: Static electricity occurs when an electric charge
builds up on the surface of an object. When certain objects are
rubbed together in a cool, dry enviroment, there is a transfer of
electrons, or negative charges. In this experiment the balloon
picks up electrons and becomes negatively charged with static
electricity.
Materials: Bubbles solution with a wand
Balloons
Bits of Paper
Procedure:
1. Blow up a balloon and tie a knot in it.
2. Blow bubbles in the air toward the balloon.
3. Draw what you observe.
4. Next, using the same balloon, rub it back and forth on the top of
your head five times.
5. Blow bubbles in the air again toward the balloon.
6. Draw what you observe.
11
Journal Questions:
1. What do you think caused the bubbles to act like they did the
2nd time? ________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
2. What happens when you rub the balloon again & hold it over
some small bits of paper? __________________________________
________________________________________________________
________________________________________________________
________________________________________________________
3. What happens when you rub the balloon again & you hold it
against the wall? _________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
4. Touch the surface of the balloon with your hand and let go.
What happens to the balloon on the wall? Why?_______________
________________________________________________________
________________________________________________________
________________________________________________________
5. What happens when you rub the balloon on a different part of
your body?______________________________________________
________________________________________________________
________________________________________________________
8. How long did the balloon hold its charges when it attracted the
bubbles and when it was on the wall?________________________
________________________________________________________
________________________________________________________
12
Bending a Stream of Water Without Touching It Experiment
Materials:
Plastic comb
Wool cloth
Thin, steady stream of water from a faucet
Procedure: 1. Rub the plastic comb with the wool cloth.
2. Bring the edge of the comb near the falling stream of water,
be careful not to wet the comb.
Observations: _____________________________________________________
__________________________________________________________________
__________________________________________________________________
Hypothesis: _______________________________________________________
__________________________________________________________________
__________________________________________________________________
READ MORE ABOUT IT!
Rubbing the comb against the wool cloth charges the comb with
static electricity. Even though the water isn’t electriclly charged by itself, a
charge is induced on the surface of the water near the comb. Since the
electricity on the comb & the induced electricity on the water surface are
opposite kinds, they attract each other. The attraction draws the water
toward the comb.
Rubbing builds up electricity on many familiar things in yor everyday life.
For example: bedsheets and other laundry items tumbled in your dryer and
become so electrically charged that they cling together and must be
peeled apart.
Conclusion:________________________________________________________
Conclusion:
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
13
Seperating Salt From Pepper Without Touching It Experiment
Materials:
Salt, Pepper(finely ground)
Plastic Spoon
Wool cloth
Paper plate
Procedure:
1. Sprinkle the salt and pepper on a paper plate and mix them together.
2. Rub the plastic spoon with the wool cloth, then hold the spoon over the
salt and pepper mixture. (Be careful not to hold the spoon too close to
the mixture).
Observations: _____________________________________________________
__________________________________________________________________
__________________________________________________________________
Hypothesis: _______________________________________________________
__________________________________________________________________
__________________________________________________________________
READ MORE ABOU IT!!
The plastic spoon becomes charged with electricity when
you rub it with the woll cloth. Both the pepper & the salt are
attracted by the electrified spoon, but the pepper rises first
because it is lighter than the salt.
The same kind of electrical attraction often causes dust
to gather on your TV screen and on charged parts inside the
set.
Conclusion:
I was able to separate the salt from the pepper without touching them
because _________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
14
Reading for Cause and Effect
Events occur because something makes them happen. What makes an event happen
is called the cause. What happens is called the effect. Examine the illustrations
below. Describe each cause and effect pair shown. Explain the relationship
between the two.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
15
You’ll Get A Charge Out of This
16
You’ll Get
Get A Charge Out of This
Study Guide for Lesson 1
Vocabulary
lightning: electricty in clouds
grounding: transfers electrical charges to the ground
protons: parts of an atom that have a positive charge (+)
electrons: parts of an atom that have a negative charge (-)
neutrons: parts of an atom that have no charge
static electricity: an electrical charge that is on something and no moving
Facts
The tiny part of an atom that has a negative charge is called an electron.
Grounding transfers electrical charges to the ground.
If an object loses some of its electrons, it will have a positive type of
charge.
Protons are parts of an atom with a positive charge.
An electrical charge that builds up on something, caused by rubbing is called
static electricity.
If two objects push each other away, then they both have the same type of
charge.
If two objects pull toward each other, then they have different types of
charges.
When an object with no charge losses electrons, it has more protons than
electrons. It is called a positively charged atom.
When an object with no charge gains electrons, it has more electrons than
protons. It is called a negatively charged atom.
If a balloon with a negative charge is brought next to a piece of wool with a
positive charge, the balloon will be pulled toward the wool.
If a balloon with a charge is held next to a balloon without a charge, the
balloons will be pulled woard each other.
Objects with no charge contain an equal number of protons and electrons.
17
Electricity Lesson II
How does electricity get to the lights in your home?
Controlling the flow of electricity is the key.
Static electricity is fun to play with, but it would be difficult to
use it to light our homes, or run our appliances. We would have to
rub things together or pull things off each other, then carry them
to where we needed to use them. Besides it is hard to make
enough static electricity to make our lights work and make our
appliances run. How do we get electricity from one place to
another ? We use current electricity.
Current electrcity is a useful form of energy because it is
easy to send it where we need it by the way it interacts with
circuits made with conductors, insulators, and resistors.
Current electricity is generated from a source, such as a
battery or generator. Current electricity is the movement of
charged particles in the same direction. Current electricity flows
along a path called a circuit.
18
Just The Facts
• A path for electricity to move through is called a circuit.
• Current Electricity is where negative charges move in conductors in one
direction. When negative charges are in motion, an electric current is
produced. Current electricity is used to power our home, factories,
appliances, and many other things. It’s called current electricity because it
moves like currents in a river or stream.
• A circuit that has no breaks or places where the current can’t flow through is
called a closed circuit. The electricity is moving, which makes a bulb light.
• An open circuit is a circuit with a break in it and there is no connection, a
bulb will not light.
• A material that has lots of avaialble electrons & allows an electrical current
to flow through it easily is called a conductor. Copper wire or aluminum
foil are examples of a conductor. Metals are conductors of electrcity. It is
dangerous to stick fingers, since the body is made up mostly of water, or
anything else in electrical sockets.
• Insulators are materials that electric current doesn’t flow through well,
causing a circuit not to work. Most plastics and rubber materials are
examples of insulators.
• A switch is a device that opens or closes a circuit. Switches are examples of
conductors and insulators. The handle of the switch, an insulator, allows you
to touch it without getting a shock. The inside of a switch is a conductor, it is
made out of metal. When switch is turned on, it creates a complete circuit
and allows electrcity to flow through it.
• A material that resists the flow of an electric current is called a resistor. The
wire inside the bulb gets very hot and you see the bulb light. A light bulb
filament is an example of a resistor.
• The unit for measuring the force that makes electrons move in an electric
current is called a volt.
• Circuit diagrams are simple drawings with symbols and lines to show the
circuit parts. People who build and design circuit use diagrams to
communicate ideas so they don’t have to draw complicated pictures.
Open Circuit
19
Closed Circuit
Lesson II
Current Events
Key Concepts For Electric Flow
Current
Circuit
The flow of electric charges
from one point to another.
An electrical path in
which a current returns to
its source.
Resistance
Opposition to the flow
of electric charges.
Conductors
Insulators
20
How Can You Make The Light Bulb Light Experiment
Objective(s):
This experiment will give students the concrete practice with the
concept that a circuit is an unintrrupted path.
• They should be able to light a flashlight bulb with a battery
and two wires.
• They should also be able to describe what happens to the
brightness of a bulb when more batteries are added.
• They should be able to infer what happens to the brightness
when more bulbs are added to the circuit with one battery.
Materials: 2 batteries
2 bulbs
2 pieces of wire
masking tape (battery holder)
pencil
Procedure: (work in pairs)
1. Using one battery & two wires , make the bulb light. Use the
masking tape or the battery holder to hold the wires in place.
2. Draw a picture to show your circuit that made the bulb light.
( Make sure to label your picture).
3. Light the bulb using two batteries
4. Draw a picture of the circuit that made the bulb light.
(Make sure to label your picture).
21
Journal Questions:
1. How did you make the bulb light each time?__________________
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
2.Where did the bulb get the energy to light from? _____________
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
3.What difference did you notice in the bulb when you use two
batteries?
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
22
23
Conductors:
A material through which electricity can flow through easily is a conductor.
The wires that carry the electricity to your home are conductors. Conductors allow
electrons to flow through it. Most metals are conductors. Aluminum and copper are
very good conductors.
Insulators:
Materials that electric current can’t flow through it easily are
insulators. Insulators restrict the movement of electrons. The electrons
are not free to move from one place to another. Wood, rubber, plastic,
and glass are examples of insulators.
It is dangerous to stick your fingers into an electrical outlet. This is because
we conduct electricity, since our body is made up of mostly water. Water is a
conductor. The electricity can flow through your body and harm you. The electric
current flowing through your house can also be dangerous if you touch any bare
wires. All the wires around your house have an insulator wrap around the
conductor. Because the insulator can be scrap off the conductor is why all the
wiring in your house is put behind walls.
24
A conductor is any item that
allows electrons to flow freely
through it. The light bulb lights up.
An insulator is any item that does not allow
electrons to flow easily through it.
The light bulb doesn’t light up.
Directions:
1. Tape the wire to the bottom of the cell.
2. Wrap the wire around the metal side of the bulb and tape it securely in
place (tip).
3. Make a prediction on each item if it will light the bulb or not. (Put a C or I
in the prediction box)
4. Make sure you place the object to be tasted between the tip of the battery
and the tip of the bulb.
5. Record your findings in the table below.
6. Put all materials back in the bags.
Item
Predication
Conductor
nail
marble
paper clip
rubber band
pins
brass fasteners
penny
nickel
eraser
crayon
pencil
paper
25
Insulator
Conductor
Insulator
How are conductors alike? ____________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
How are insulators alike? _____________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
Conclusion: ________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
26
Materials
3 pieces of electric wire
1 D cell
1 bulb and bulb holder
Paper clip
Masking tape
Wooden board with two screws inserted on it
Procedure
1. Put one end of the paper clip around one of the screws on the board.
2. Connect the wires as shown, winding them around the screws once or twice.
3. Make sure the bulb is screwed into the bulb holder
4. Close the switch by moving the paper clip so that it touches the screw that it
isn’t attached to.
What happen when you touch the paper clip to the other screw? _______________
__________________________________________________________________
What type of circuit did you make an open or closed circuit? _________________
__________________________________________________________________
__________________________________________________________________
What happen when the paper clip didn’t touch the other screw? _______________
__________________________________________________________________
What type of circuit did you make an open or closed circuit? _________________
__________________________________________________________________
__________________________________________________________________
Explain how your switch works.________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
27
The bulb won’t light in the circuit above. What’s wrong with the circuit? It
has a gap. How could you fill the gap to make a closed circuit? The easiest way
would be to connect the two wires together, but with what?
What would happen if you placed a paper clip across the gap? How about a
nail? The bulb would light. The nail and paper clip carry, or conduct, electricity.
They are both conductors.
Some materials will not carry the electricity well enough to make the bulb
light. Try a rubber band. The bulb won’t light. Rubber is a poor conductor of
electricity, it is called an insulator.
Find the different materials hidden in the word search below. Place the words you
find in their correct group.
COTTONP
OKGTSOR
PAPERXK
PLASTIC
EUDTORD
RMKELOS
TIXERNN
NNGLASS
RUBBERZ
KMGRXZP
Insulator
________________
________________
________________
________________
________________
Conductor
__________________
__________________
__________________
__________________
Place a C if picture is a conductor or an I if picture is an insulator.
_________
_________
________
28
__________
29
Electricity flows through a pathway called a circuit.
To learn more about the flow of electricity, complete each sentence with the
words from the box.
Open Circuit
Closed Circuit
• a source, through wires, and back to the source.
• that allows electricity to pass through easily.
• an incomplete pathway.
• the circuit must be closed
• to open and close a circuit.
• through an open circuit.
• not allow electricity to flow through easily
• can be controlled by switches
•
1. In order for electricity to flow _____________________________________________________
______________________________________________________________________________
2. A closed circuit is a complete pathway from _________________________________________
_______________________________________________________________________________
3 Electricity can’t flow ____________________________________________________________
_______________________________________________________________________________
4. An open circuit ________________________________________________________________
_______________________________________________________________________________
5. The flow of electricity ___________________________________________________________
_______________________________________________________________________________
6. A switch is a device that is used ___________________________________________________
_______________________________________________________________________________
7. A conductor is a material _________________________________________________________
________________________________________________________________________________
8. An insulator does _______________________________________________________________
30
31
Current Events Review
32
Current Events
Lesson II Study Guide
A path for electricity to move through is a circuit.
A type of electricity in which charges move in conductors is called current
electricity.
A circuit that has no breaks or places where the current can’t flow is called
a closed circuit.
A material that has lots of available electrons and that allows an electrical
current to flow through it easily is a conductor.
A light bulb filament is an example of a resistor.
Tools are usually covered with rubber because rubber is an insulator. An
insulator is a material that doesn’t allow electrcity to flow through it easily.
Having rubber on tools made out of metal helps prevent an electrical current
from flowing through the metal tool and giving the worker a shock.
A wall switch controls if the lights are on or off. If the switch is “on” it
allows electric current to flow through the circuit and makes the lights
work. If the switch is turned “off” it cause a break in the circuit and
prevents the circuit from flowing throuh it. The lights are off.
Be able to label the parts of a light bulb and circuit diagram.
The circuit diagram is an open circuit because
there is a break in the flow of electricity. The
switch is open.
33
Electricity Lesson III
At home, do you have two or more lamps or other electrical devices that are
tuned on and off by the same switch? When one lamp or appliance stops working,
do other lamps or appliances also stop working? Do all the electrical devices in the
house go out? Sometimes you want to turn on more than one light bulb with one
switch. You may even want to light a bulb with more than one cell (battery). How
do you think this is done? Have you ever wondered why all the lights in a sports
stadium come on at once?
You can’t see them, but there are wires running through your house, to all
your wall outlets, and switches. If each one of these have their own circuit, why do
several devices and lights go out when there is a problem? Shouldn’t only one
appliance or light with a problem go out?
In the previous lesson, you learned about open and closed circuits, and
switches. In this lesson you will take this knowledge and apply it to how more
complex circuits work. You will understand the concept that an electrical circuit is
a system with all the parts of that circuit working together and doing their own
jobs. All the circuits in a building, school, and your house are connected to make
the electrical system of these structures.
You learned that electrical circuits provide a pathway for the electricity
(electrons) to flow from the battery (cell) through the device (bulb) then back to
the battery (cell). There are many different kinds of circuits. In this lesson you will
learned about series and parallel circuits.
You will learn how they differ in usefulness in supplying energy to your
house and appliances. Safety devices, such as fuses and circuit breakers will also
be discussed.
34
Just The Facts – Study Guide
• Something that allows you to stop or start the flow of current through a
circuit is a switch.
• A short circuit is when there is practically no resistance in a circuit. The
electric current “skips” the rest of the circuit. This happens when frayed or
broken wires touch. Too much current flows through wires and the electric
current heats up the wire.
• A series circuit is a circuit where electrons are given one path to follow. A
break in any part of the circuit interrupts the flow of electrons to parts of the
circuit. The electrical current moves through the parts of the circuit one
after another. A light or bulb is dimmer in a series circuit.
• A parallel circuit is a circuit where electrons can follow several paths. If a
break occurs in one part of the this circuit, electrons can continue to flow by
following a different path. The electrical current flows through both parts of
the circuit at the same time. A light or bulb is brighter in a parallel circuit.
• A safety device that has a thin strip of metal in it is called a fuse. If there is
too much current flowing through a circuit, the strip of metal melts and
opens the circuit. The fuse must be replaced to restore the power.
• Like a fuse, a circuit breaker opens the circuit and cuts the power supply to
your house. A circuit breaker’s switch must be flipped close to restore the
power.
Fuses
Circuit Breaker
Short Circuit
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Series circuit
In a series circuit, the electric current flows through each bulb, one bulb after
another, when the circuit is complete (the switch is closed). The bulbs connected in
this circuit will not be bright because the have to share the electricity flowing
through the circuit. Also, all of the electricity available must flow through each
bulb as it moves along. This creates more resistance and less electricity flowing in
the circuit. The brightness of the bulbs depends on how much electricity each bulb
receives. If one bulb in the series circuit goes out, or if you unscrew one bulb, the
circuit is broken and all the bulbs go out. In a series circuit, either everything is on
or everything is off. Some Christmas lights are a good example of lights wired in a
series circuit.
Parallel circuit
In a parallel circuit, the current flows in more than one path. Each bulb has
its own supply of electricity. If one bulb in the parallel circuit goes out, or if you
unscrew one bulb; the rest of the bulbs will stay on. This is because each bulb has
its own supply of electricity and it doesn’t have to wait for the electricity to pass
through one bulb before it gets to another one. Because of this, lights wired in a
parallel circuit burn brighter than lights wired in a series circuit. Parallel circuits
are used to wire your home, buildings, and school.
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Electric Circuits
How does the flow of electricity in a series circuit differ
from the flow of electricity in a parallel circuit?
Build a series circuit like the picture shown:
1. What happens when you remove a bulb?
Prediction
_______________________________________
_______________________________________
_______________________________________
Results
_______________________________________
_______________________________________
_______________________________________
Build a parallel circuit like the picture shown:
2. What happens when you remove a bulb?
Prediction
______________________________________
______________________________________
______________________________________
Results
______________________________________
______________________________________
______________________________________
3. In which kind of circuit did the bulb glow more brightly?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
4. Conclusions
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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Electric Circuits –Part 2
Here is a schematic drawing of an electric circuit. Electricians
use diagrams like this when they put electric circuits into
houses and other buildings.
1. Build a circuit using this diagram above as a plan. Use a dry cell (battery) for
your power supply and a bulb for your load.
Notice that there is a switch. When the switch is open, the circuit is broken (open
circuit). If you do not have a switch for your circuit, what else can you do to break
the circuit and turn off the light? ________________________________________
__________________________________________________________________
2. Now make another circuit. After you have built it, make a schematic drawing of
it like the one above, in your science journal. Make sure you label all the parts.
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A
B
You can light several light bulbs with only one cell (battery). In picture A, the
bulbs are connected in a series circuit. What would happen to the circuit if you
unscrewed one bulb? ______________________________________
In picture B, the bulbs are connected in a parallel circuit. What would happen if
you unscrewed one bulb? ___________________________________
Dry cells (batteries) can also be connected in a series and parallel circuits.
However, cells are usually connected in a series. A series of cells increase the
amount of power that flows in a circuit. A series of cells will make the light bulb
burn brighter.
1. In what picture above are the cells connected in a series? __________________
2. In which picture above will the bulb light more brightly? __________________
3. If a light burns out on your Christmas tree, and the rest of the lights go out
also. What kind are the bulbs connected? _______________________________
4. How do you think the electric lights in your house are wired? Series
circuit or Parallel circuit? Why? ______________________________________
_________________________________________________________________
5. How are the batteries connected in the flashlight below? Series or Parallel?
________________________________________________________________
6. If we added one more cell to this flashlight, what would happen to the
brightness of the bulb? ______________________________________________
_________________________________________________________________
Fun Fact:
A single dry cell is often called a battery, but it really isn’t a battery. A
battery is two or more cells connected together. You can buy batteries that
look like a single cell, but they are really two or more cells connected together
and put inside one case.
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Safety Rules
1. Unplug appliances by pulling on the plug, not the cord.
2. Don’t plug too many appliances into one outlet.
3. Don’t use an appliance near water, outside on damp ground, or
4.
5.
6.
7.
8.
when your hands and feet are wet.
Never used an appliance with a damaged cord.
Don’t fly a balloon or kite near electrical wires.
Never touch a fallen electrical wire.
Don’t experiment with electrical wires.
Never stick anything metal in an electrical appliance or outlet.
Electricity is useful to us, but it can be very dangerous. If a person becomes part of an
electrical circuit, they can receive a shock strong enough to kill them. Electricity can also start
fires. Fortunately, there are devices that protect us from electrical hazards. Fuses and circuit
breakers can be wired into the circuits in buildings, homes, and schools. These special switches
automatically open the circuit if it is overloaded and stop the flow of electricity before the wires
get too hot. A lightning rod is a metal rod mounted on top of the building. A heavy wire
connects it to a piece of metal buried in the ground. The rod attracts lightning, and the electricity
is carried through the wire safely into the ground instead of through the building, school, or your
house.
Answer each question in a complete sentence.
1. What is a lightning rod? _______________________________________________
_____________________________________________________________________
2. What are two hazards of electricity? ______________________________________
_____________________________________________________________________
3. What do fuses & circuit breakers do? _____________________________________
_____________________________________________________________________
4. How does a person get an electrical shock? ___________________________
___________________________________________________________
5. Why would it be dangerous to fly a kite near electrical wires? _________________
_____________________________________________________________________
6. Does water conduct electricity? List the rule from above that helped you answer this
question. _____________________________________________________________
_____________________________________________________________________
40
Lightning
Lightning is a very interesting phenomenon of nature. It is a huge electrical
spark. We usually see it going from a cloud to the ground, but it also travels
between two clouds, within a cloud, and even from a cloudinto the air.
During a storm, many actions are taking place. Wind is blowing, water is
freezing, and ice is melting. Raindrops are forming, dividing, and being blown
by the wind. Ice crystals and raindrops collide and become positively or
negatively charged. Latest research shows that the positively charge
particles gather near the top and bottom of the cloud, while the negatively
charged particles are sandwiched in between.
The cloud’s lower negative particles induce a positive charge on the earth’s
surface. When the voltage in the coud is large enough to ionize the air and
make it a condutor, the built up negative charges surge toward the earth in a
series of faint, jagged streaks known as leaders.
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Since opposite charges attract each other, these positive charges surge up
to meet the leaders’ negative charges. This surge continues upward,
retracting the leader’s paths back to the cloud in bright return strokes we
see and call “lightning.”
Although each flash of lightning lasts only about a millionth of a second, it
has a huge amount of electric current in it. Some single flashes have been
measured at over 300,000 amps of electricity, enough to light about
200,000 homes. The light from these return strokes of lightning travel at
the speed of light (300,000 kilometers per second), while the electrical
charges in them move just a bit more slowly.
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As lightning travels through the air, it heats the air in its path to over
60,000 degrees, Fahrenheit. This superheated air expands very quickly,
producing a wave of pressure that causes thunder.
Since lightning strikes somewhere on the earth about
100 times each second, there are frequent
opportunities to study it. Because we know more and
more about the conditions under which lightning is most
apt to happen, high-speed cameras have been designed
to sense these conditions and automatically photograph
the lightning when it happens.
Although many scientists have investigated what it is and how it works,
lightning is still very difficult to analyze and understand. This is because
the information related to it ranges from the action of tiny atoms to the
production of huge amounts of heat and light. This is why you may read
conflicting information in different books. Since scientists are discovering
more and more about lightning all the time, reading current magazines like
Scientific American is a good way to get the latest accurate information.
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Lightning Sequence Activity
Number these diagrams in proper sequence.
44
45
46
Down the Line Review
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Down the Line
Lesson III Study Guide
Something that allows you to stop or start the
flow of current through a circuit is a switch.
When there is practically no resistance in a circuit,
it is called a short circuit.
A fuse is a safety device that has a thin strip of
metal in it. If there is too much current flowing
through a curcuit, the strip of metal melts and
opens the circuit.
Lightning is electricity in the clouds.
A circuit breaker opens the circuit to keep excess current from flowing
through the wires.
In a series circuit, the electric current has only one path and flows through
each bulb, one bulb after another.
In a parallel circuit, the current has more than one path and flows through
each bulb separately.
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