Lesson 4 Types of Energy - Home - SchoolMessengernewlondonscs.sharpschool.com/UserFiles/Servers/Server...much energy? Types of Energy Theater of Electricity, Museum of Science, Boston

A Van de Graaff generator can create giant arcs of electrons. How could you control this much energy?

Types of EnergyTheater of Electricity, Museum of Science, Boston

Lesson 4

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114ENGAGE

PS.13 Investigate how changes in the position of a light source and an object alter the size and shape of the shadow (PS-M-C4) PS.14 Identify other types of energy produced through the use of electricity (e.g., heat, light, mechanical) (PS-M-C6)Also covers PS.12

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How does light move away

from its source?

Make a PredictionOn what kind of path does a light beam travel? How many mirrors are needed to bend a light beam around an obstacle? Make a prediction.

Test Your Prediction

Make a Model Trace the outline of a flashlight’s face on a piece of construction paper. Cut out the shape, and make a small hole in the center.

Be Careful. Tape the cutout over the face of the flashlight. Fold a second sheet of construction paper in half. Set it in a lump of clay at one end of a meterstick as a target. Darken the room.

Observe Hold the flashlight at the other end of the meterstick. Aim the beam at the target. Blow powder into the beam to make it more visible. Compare the beam’s path to the meterstick. What is the shape of the light beam’s path?

Experiment Block the beam of light from reaching the target. Fold a piece of construction paper in half. Set it in a piece of modeling clay, and attach the clay to the middle of the meterstick. Using mirrors, can you bend the light beam to reach the target? Are one or two mirrors needed to get the beam to the target?

Draw Conclusions

Interpret Data Could you make a light beam follow a curved path? How could you change a light beam’s path?

Explore More

What would you do if you wanted the light beam to hit the back of the target? How many mirrors would you need? Design an experiment to test your prediction.

• flashlight

• 3 pieces of construction paper

• scissors

• tape

• modeling clay

• meterstick

• talcum powder

• 2 mirrors

• flashlight

• 3 pieces of constructionpaper

• scissors

• tape

• modeling clay

• meterstick

• talcum powder

• 2 mirrors

Step

Step

Materials

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115EXPLORE

SI.14 Develop models to illustrate or explain conclusions reached through investigation (SI-M-A5) SI.23 Use relevant safety procedures and equipment to conduct scientific investigations (SI-M-A8)Also covers SI.4

s


▶ Essential QuestionWhat are different types of energy?

▶ Vocabularyelectrical energy, p. 116

thermal energy, p. 116

mechanical energy, p. 117

circuit, p. 118

electric current, p. 118

shadow, p. 122

solar radiation, p. 124

▶ Reading Skill

Summarize

Summary

▶ Technology e-Glossary and e-Review onlineat www.macmillanmh.com

PS.13, PS.14

How do we use different types of

energy? Think about all the things you do that require

energy. You might turn on lights, listen to music, work at a computer, or ride in a car or a bus. Energy makes motion and change possible. Energy can be changed, or transformed, from one type into another type. Most types of energy on Earth originate with the Sun. What are some types of energy that you use?

Electrical Energy

People depend on electrical energy to cook food, light rooms, and power computers and air conditioners. Electrical energy is the energy that comes from the movement of charged particles. Some electrical energy comes from batteries. However, most of it comes from power plants that burn fuel to make electricity. The electrical energy is sent through wires and cables to homes and businesses. Electrical devices change this energy into other kinds of energy, such as thermal, light, and mechanical.

Thermal Energy

A lit candle has a higher amount of thermal energy than an ice cube. Thermal energy is the energy due to the motion of particles in matter. Both objects give off heat, but the candle gives off much more than the ice cube. Recall that heat is the flow of energy between objects. The faster the particles move, the warmer a substance gets. The more thermal energy a substance has, the warmer the substance is.

Electrical energy can be converted into heat. This heat can be used to cook food and dry clothes. Some furnaces use electrical energy to heat homes. Inside a hair dryer, electrical energy passes through wires. This causes the wires to heat air inside the hair dryer.

◀ Power lines are used to transmit electricity. The wires are copper or aluminum because these metals allow electricity to flow easily.

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116EXPLAIN


Light Energy

The Sun is the main source of light energy on Earth. When plants make food through photosynthesis, they convert sunlight into chemical energy.

Electrical energy can also be a source of light. Inside an incandescent bulb is a thin wire called a filament. As the filament resists electric current, it heats up and glows. The electrical energy is converted to light and heat energy.

Mechanical Energy

Mechanical (mih•KA•nih•kul)

energy is the sum of kinetic and potential energy. Moving objects have mechanical energy.

Electric motors change electrical energy into mechanical energy in toys, washing machines, drills, and other tools.

Other Types of Energy

Chemical energy is stored in the particles that make up food and other fuels. When you eat food, chemical energy passes to you. When you move, your muscles change the chemical energy from the food you ate into mechanical energy.

Nuclear energy is potential energy stored in the links between protons and neutrons in an atom. The nuclear energy of the Sun becomes forms of energy such as light. This provides energy for Earth.

Quick Check

Summarize Name the different types

of energy. Give an example for each.

Critical Thinking What do all types of

energy have in common?

electrical energy changinginto heat energy

electrical energy changing into light energy

light energy changing into chemical energy

chemical energy changing into mechanical energy

Which energy change is needed for life?

Clue: The Sun is Earth’s primary source of energy.

Read a Photo

Energy Transformations

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117EXPLAIN


How can electricity flow?When you’re in the dark, a flashlight is useful. Electrical

energy changes to light energy and the bulb lights up. The flashlight forms a circuit that allows electric current to flow.

A circuit (SUR•kut) is formed when an electric current passes through an unbroken path of conductors. Electric current is the flow of electricity through a conductor. Often the path of a circuit consists of wires. Circuits must also have a device to move electrons along the path. These devices, called voltage sources, increase the strength of electrons moving in the circuit. Batteries are a voltage source.

A switch is a device that can open or close the path. When the switch is closed, the voltage pushes on the electrons in the circuit. This causes electrons to move. Protons feel a force in the opposite direction. However, protons are not free to move.

Electricity does not flow the same way through every part of a circuit. An object in an electrical circuit that resists the flow of electrons is called a resistor (rih•ZIS•tur). Electrons lose energy when moving through a resistor. This energy can be transformed into heat or light. A lightbulb is a resistor.

Electrons may not travel far in a circuit. SI.18

Electric Circuit

Where does electrical energy change form in this circuit?

Hint: Where is the resistor?

Read a Diagram

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118EXPLAIN


Electric current in a circuit travels fast—almost at the speed of light. Electrons, however, travel just a few millimeters per second. Why? Electrons only need to move far enough to push another electron. That electron then pushes another and so on.

The amount of electric charge moving in a circuit is measured in units called amperes (A), or amps. There are about 6 billion billion electrons moving every second in 1 amp of current. Even currents as small as 0.05 A can seriously harm you.

Measuring Electric Current

Build a flashlight circuit using a battery, a switch, and a lightbulb.

Observe Close the switch and record your findings.

Open the circuit and add another battery. Make sure the positive end of one battery touches the negative end of the other.

Close the switch again. Is the lightbulb the same brightness as before? Why?

Infer When was there more electricity flowing through the circuit? How do you know?

SI.16

Quick Check

Summarize How does energy

change form in a flashlight?

Critical Thinking How is the

resistance of a resistor similar to

friction?

electrons

battery

Electricity flows in a wire like water flows in a hose.

h again. Is the me brightness as

s there more ng through

w do you know?

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119EXPLAIN


What is light? Light from the Sun travels more than 90 million miles to

Earth in only 81

33 minutes! Light is made of vibrating electrical and magnetic energy. This energy travels as a wave. Light waves vibrate in the direction perpendicular to the direction of their motion. They are called transverse (trans•VURS) waves.

Light does not travel in the same manner as other waves, such as sound waves. Most waves require a medium, or substance, through which to travel. Light waves, though, can travel with or without a medium. In a vacuum, light travels very fast—about 300,000 km/s (186,000 mi/s). Light travels slightly slower through mediums like air, water, or glass. In glass, for example, light travels about 197,000 km/s (122,000 mi/s). The speed of light is so fast that some scientists think nothing travels faster.

Wavelength (WAYV•length) is the distance between one peak and the next in a wave. Frequency refers to how many wave peaks pass a given point in one unit of time, such as a second. When you multiply the wavelength of a wave by its frequency, you get the speed of that wave.

Light is a wave made from electrical and magnetic energy.

electric wave

magnetic wave

wavelength

direction of travel

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120EXPLAIN


Light Is Also a Particle

Although light is a wave of energy, it is also a particle. How can something be both a wave and a particle? Scientists were confused about this question for a very long time. They performed many experiments and found that light has properties of both waves and particles, so they concluded it was both.

Light is like a particle in several ways. It travels in straight lines called light rays. Light does not have mass like a particle, but it does have momentum like a particle. When light hits an object, it acts like a tiny particle. Light can even change the direction of atoms and other small particles. Another way that light acts as a particle can be seen in camera film. When light hits camera film, it produces little dots. Over time, those dots will eventually form the original image.

Particles of light are called photons (FOH•tahnz). A photon is a tiny bundle of energy by which light travels. The energy of a single photon is very small: a photon of red light has only about 0.0000000000000000003 J of energy! Each photon also acts like a wave with a frequency. If a photon has a higher frequency, it also has more energy.

Quick Check

Summarize What properties of

particles does light have?

Critical Thinking How could you

find the wavelength of light if you

knew its speed and frequency?

Photons hit a piece of film individually. When enough of them have hit, the image the camera took appears.

Light is both a wave and a particle. SI.18

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121EXPLAIN


How does light make

shadows?When light strikes an object’s

surface, photons bounce off at random angles. This is called scattering (SKA•tuh•ring) light. We see objects because light has scattered off them and entered our eyes.

Sometimes when light hits an object, a photon is absorbed, or taken in. These objects gain energy. The light that is absorbed is usually transformed into heat energy. Darker objects absorb more light than lighter objects.

Light may also pass through objects. Recall that objects that allow most light to pass through are called transparent.

Objects that blur light as it passes through are called translucent. If an object allows little to no light to pass through, it is called opaque.

Whether an object is opaque, translucent, or transparent depends on its material, its thickness, and the color of the light. Thicker objects have more particles to absorb photons, so they are more likely to be opaque. Some objects will be opaque, transparent, or translucent in only one color of light.

Opaque and translucent objects block light. The area behind these objects is darker—they have a shadow. A shadow is a dark area produced when an object blocks the passage of light.

Translucent objects blur light that passes through.

Opaque objects let little to no light pass through.

Transparent objects allow almost all light through.

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122EXPLAIN


When an object is between a light source and another object, it will cast a shadow on the other object. Light sources can be natural, such as the Sun, or artificial, such as a flashlight.

You cast shadows on the ground when the Sun shines. Have you ever seen how long your shadow is at sunrise? The Sun is low in the sky. Light from the Sun travels toward you at a low angle. At this angle, there is a long distance before the sunlight hits the ground behind you. As the Sun rises, the angle of the sunlight increases. This shortens your shadow. When the Sun is directly overhead, around noon, your shadow is at its shortest.

Shadows depend on the angle and the distance between a light source and an object, and between the object and the place where the shadow is cast. Drawing light rays shows the angle of the Sun in relation to Earth. The closer a light source is to an object, the larger the shadow an object will cast.

You can find the size and shape of a shadow by tracing light rays.

Quick Check

Summarize What are the ways in

which light interacts with matter?

Critical Thinking What makes a

white shirt cooler than a dark one

on a sunny day?

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123EXPLAIN


How is the Sun an

important energy

source?The Sun is Earth’s primary source

of energy. At any given moment, the Sun is shining on some part of Earth’s surface. Sunlight warms the surface of the planet. The heat from the Sun causes air currents and water currents to form. On Earth, living things require the Sun’s energy to carry out everyday life functions.

Energy from the Sun that reaches Earth’s surface is known as solar radiation. Plants use it to carry out photosynthesis. They convert solar radiation to chemical energy, which can be used by other organisms. The food we eat, the gasoline we use to power our vehicles, and much of our clothing and other materials would not exist without the Sun’s energy.

Energy from the Sun also affects nonliving things. Solar energy influences a region’s weather and climate. Solar energy drives the water cycle, or the continual movement of water between Earth’s surface and the air. Energy from the Sun helps to recycle Earth’s supply of water, which is essential to life.

Quick Check

Summarize How do animals

obtain energy from the Sun?

Critical Thinking What are

some other reasons the Sun is an

important energy source?

▲ Plants use photosynthesis to convert the Sun’s energy into chemical energy, which is then taken in by other organisms, such as this giraffe.

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124EXPLAIN


Think, Talk, and WriteVocabulary A material or an object that blocks light completely can create a .

Summarize List different types of energy and give examples of each.

Summary

Critical Thinking How could you make the shadow of a small child have the same height as the shadow of an adult?

Test Prep A stereo performs which of the following energy conversions?A electrical energy to light energyB sound energy to electrical energyC electrical energy to sound energyD electrical energy to chemical energy

Test Prep Which energy source makes photosynthesis possible?A electricityB the SunC other plantsD gasoline

Essential Question What are different types of energy?

Visual Summary

Make a Study Guide Make a trifold table. Use the titles shown. Summarize what you have learned in the boxes provided.

Personal NarrativeWrite a few paragraphs in your science

learning log about ways you use energy.

Be sure to identify the type of energy,

such as light energy, mechanical energy,

electrical energy, and so on.

Hand ShadowsUse your hands and a flashlight or lamp

to make shadows. Try to make different

shapes. Move the light source and your

hand closer and farther away from each

other. What happens to the shadows?

Writing Link Art Link

-Review Summaries and quizzes online at www.macmillanmh.com

Electrical energy can be used to produce other forms of energy, such as light, heat, or mechanical energy.

The size and shape of a shadow depends on the angle and distance between a light source and an object.

The Sun is the primary source of energy for Earth, powering photosynthesis and the water cycle.

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125EVALUATE


Inquiry Skill: Use VariablesHave you ever made shadow

puppets? Shadow puppets are images that you make on a wall. The shadow images can move, get larger, or get smaller depending on how you move your hands in relation to the light source. How does the distance of an object from a light source affect the size of the shadow that forms? To answer a question such as this, scientists use variables by doing a set of experiments.

▶ Learn ItWhen you use variables you change

one factor at a time and see how it affects the outcome of the experiment. The factor that is changed is called the independent variable. The outcome of the experiment is called the dependent variable.

For this investigation there will be two independent variables—the distance from the object to the shadow and the distance from the light source to the object. Each independent variable will be tested in a separate experiment to determine the effect on the dependent variable—the area of the object.

▶ Try ItMaterials flashlight, tape, pencil,

poster board, ruler, small rectangular classroom object

Make two tables like those shown to record your data.

Tape a piece of poster board to a smooth wall. Have a classmate hold a small object 5 cm in front of the paper. Hold a flashlight 10 cm in front of the object so that its shadow appears on the poster. Have another classmate trace the shadow that forms. Measure the area of the shadow by multiplying its length by its width and record it in your data table.

Now repeat the experiment, changing the distance from the object to the poster using the distances in the first table.

What will happen if you change the position of the flashlight while keeping the distance from the object to the poster constant? Use the distances in the second table and record your results.

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126EXTEND

PS.13 Investigate how changes in the position of a light source and an object alter the size and shape of the shadow (PS-M-C4) SI.9 Use computers and/or calculators to analyze and interpret quantitative data (SI-M-A3)tt

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Independent Variable: Object to Poster Distance

Flashlight toObject Distance

10 cm10 cm10 cm10 cm

5 cm10 cm15 cm20 cm

Object toPoster Distance

Area ofShadow (cm2)

Independent Variable: Flashlight to Object Distance

Flashlight toObject Distance

5 cm10 cm15 cm20 cm

10 cm10 cm10 cm10 cm

Object toPoster Distance

Area ofShadow (cm2)

▶ Apply It Now use a computer spreadsheet program to analyze your data. Enter your data into two separate tables in the spreadsheet.

Create two line graphs. On one you will have the distance from the object to the paper as the x-axis (horizontal axis) and the area of the shadow on the y-axis (vertical axis). On the other you will have the distance from the light source to the object on the x-axis and the area of the shadow on the y-axis.

How did the size of the shadow change when each of the two independent variables was changed?

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127EXTEND

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Lesson 4 Types of Energy - Home - SchoolMessengernewlondonscs.sharpschool.com/UserFiles/Servers/Server...much energy? Types of Energy Theater of Electricity, Museum of Science, Boston

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