Just the Facts. Green balloon pulling toward red balloon. Orange balloon is being pulled toward the wool.

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1 Electricity!! What comes to your mind when you read about this word? Do you think about your video game? A lightning storm? The lights of your city in the night? You use electricity when you turn on the lights. You also 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

2 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

3 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 very, very tiny pieces called atoms. An atom is made up of smaller particles called protons, electrons, and neutrons. These particles have a property called a charge. All electricity is caused by charges. Some have a positive charge (protons protons); others have a negative charge (electrons electrons). Most of the time, the number of charges is equal (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

4 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

5 _ _ 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

6 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

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8 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

9 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 / meters 135 feet / meters 7,063,000 cu. feet / 211,890 cu. meters Four 1200 hp Mercedes Benz engines 84.4 mph / 135 km/h Hydrogen 9

10 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

11 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

12 Journal Questions: 1. What do you think caused the bubbles to act like they did the 2 nd 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

13 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: 13

14 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

15 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

16 You ll Get A Charge Out of This 16

17 You ll 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

18 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

19 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 Closed Circuit 19

20 Lesson II Current Events Key Concepts For Electric Flow Current The flow of electric charges from one point to another. Circuit An electrical path in which a current returns to its source. Resistance Opposition to the flow of electric charges. Conductors Insulators 20

21 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 masking tape (battery holder) 2 bulbs pencil 2 pieces of wire 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

22 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

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24 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

25 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 Insulator nail marble paper clip rubber band pins brass fasteners penny nickel eraser crayon pencil paper 25

26 Conductor Insulator How are conductors alike? How are insulators alike? Conclusion: 26

27 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

28 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 Insulator Conductor OKGTSOR PAPERXK PLASTIC EUDTORD RMKELOS TIXERNN NNGLASS RUBBERZ KMGRXZP Place a C if picture is a conductor or an I if picture is an insulator. 28

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30 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

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32 Current Events Review 32

33 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

34 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

35 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 35

36 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. 36

37 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 37

38 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. 38

39 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. 39

40 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 when your hands and feet are wet. 4. Never used an appliance with a damaged cord. 5. Don t fly a balloon or kite near electrical wires. 6. Never touch a fallen electrical wire. 7. Don t experiment with electrical wires. 8. 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

41 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. 41

42 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. 42

43 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. 43

44 Lightning Sequence Activity Number these diagrams in proper sequence. 44

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47 Down the Line Review 47

48 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. 48