Big Idea 6. Day 1. Weekly Question How do windmills make electricity?

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1 1 The universe runs on many types of energy. Mechanical energy is the energy of a movable object. Thermal energy is internal energy produced by the vibrations of a substance s molecules. Chemical energy is contained in the chemical bonds of molecules. And the type of energy that windmills generate is electrical energy, or electricity, which is produced by the movement of electrons between atoms. Each type of energy exists in two forms: kinetic energy and potential energy. Kinetic energy is the energy of motion. Potential energy is stored energy, or the energy of position or condition. A good example is a stretched rubber band. As a result of the condition of being stretched, energy is stored in the rubber band. When you release it, the potential energy is converted to kinetic energy as the rubber band snaps back. Types of Energy mechanical thermal chemical electrical A. Identify each type of energy as chemical, electrical, mechanical, or thermal. energy usable power; the ability to produce a change in matter kinetic energy kih-neh-tik the energy of motion potential energy poh-ten-shul stored energy due to position or condition 1. the energy produced by a ball rolling on the floor 2. the energy contained in food molecules 3. the energy in an electrical outlet 4. the energy in a hot oven B. Identify each example as representing kinetic energy or potential energy. 1. water held in a dam 2. ocean waves crashing on the shore Evan-Moor Corp. EMC 5016 Week 1 159

2 2 For thousands of years, people have used windmills for a variety of purposes, such as grinding grain and pumping water. These days, most windmills are used to generate electrical energy. Windmills that produce electricity are called turbines. Turbines do not create electricity out of thin air. Rather, they take energy that already exists in one form and convert it to another. The energy that is ultimately used by turbines begins as solar energy, or energy from the sun. Solar energy is absorbed by the surface of Earth as thermal energy, which heats the air close to the ground. When the warm air rises, cold air rushes in to fill the space. This creates wind, which is a form of mechanical energy. By harnessing the power of the wind, turbines convert mechanical energy to electrical energy. turbines TER-bynz windmills that produce electricity Dutch windmill American windmill turbine A. List one similarity and two differences among the windmills above. Similarity: Differences: B. In order for windmills to make electricity, energy is transformed from one type into another. Write the types of energy in the correct order. C. Fill in the bubble next to the word that completes the sentence. Turbines convert energy to electricity. A solar B thermal C mechanical D electrical electrical energy 160 Week 1 EMC 5016 Evan-Moor Corp.

3 3 Wind blowing against the blades of a turbine produces mechanical energy. The blades are tilted at an angle to channel the air, and this causes them to rotate. Inside the turbine, a device called a drive shaft connects the blades to a generator, a machine that converts the mechanical energy created by the moving blades to electrical energy. A generator uses electromagnetism to produce electricity. The generator has a huge magnet that surrounds coils of copper wire. The rotating blades of the turbine turn the drive shaft, which causes the metal coils inside the generator to spin between the positive and negative poles of the magnet. When metal such as copper moves through a magnetic field, an electric current, or the flow of electricity, is produced. electromagnetism ee-lek-troh-magneh-tih-zum the interaction between an electric current and a magnetic field A. Use information in the passage to label the parts of the windmill below. Use the words blade, magnet, drive shaft, and metal coils. B. In your own words, summarize how a generator uses electromagnetism to produce electricity. Evan-Moor Corp. EMC 5016 Week 1 161

4 4 When the copper metal and giant magnet of a windmill s generator interact, electrons in the metal wires start to flow. Electrons generate an electric field as a result of their negative charge. They also generate a magnetic field as a result of their motion. The electric and magnetic fields of an electron combine, each one encouraging and strengthening the other. Thus, moving electrons are electromagnetic. Windmills use this force to produce electrical energy. Electrical energy from a windmill is transported to power plants and homes along metal wires. Metals are good conductors of electricity due to their structure. A metal atom is big, so its nucleus has only a weak hold on the atom s outer electrons. When many metal atoms come together, their outer electrons break out of their orbitals to form a sea of electrons that move freely from atom to atom. All of the free electrons moving in the same direction produce an electric current. field feeld an area in which a force or influence occurs Answer the questions. 1. Which kind of field is produced by electrons as a result of their charge? 2. Which kind of field is produced as a result of the motion of electrons? 3. What does the structure of metal atoms have to do with their ability to conduct electricity? 4. How is electricity transferred from windmills to homes? 162 Week 1 EMC 5016 Evan-Moor Corp.

5 5 A. Use the words in the box to replace each underlined phrase. potential energy turbines electromagnetism kinetic energy energy field 1. The ability to cause a change in matter takes many different forms. 2. A compressed metal spring is an example of the energy of position. 3. A generator uses the interaction between electric and magnetic fields to produce electricity. 4. The energy of motion can be visible, such as when a jet flies overhead, or invisible, such as when water evaporates. 5. A wind farm is a group of windmills that generate electricity. 6. A magnetic area in which a force occurs is caused by electrons in motion. B. Next to each clue, write whether it provides an example of electrical energy, mechanical energy, chemical energy, or thermal energy. 1. melting ice 2. a rusting nail 3. spinning blades of a windmill 4. a shock from touching a doorknob Evan-Moor Corp. EMC 5016 Week 1 163