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Name ______________________________ Lesson 2 Summary Use with pp. 14–19 Lesson 2: How do electric charges move? Vocabulary electric current electric charges in motion resistance a property of a material that does not allow electric current to flow easily through it series circuit a circuit in which electric charge can flow only in one path Electric charges that move or flow form an electric current. Sometimes the direction and flow of current is controlled. The current follows a path. This path is called an electrical circuit. A closed circuit is a complete loop, or a whole circle. It has no breaks. A current can flow through a closed circuit. An open circuit has one or more breaks. A current cannot flow through an open circuit. Conductors, Resistors, and Insulators A conductor is a material that allows electricity to flow easily. The wires, clips, and switches in a circuit are conductors. A resistor is a material that resists the flow of electric current. Resistance means that the material does not allow electric current to flow easily. Resistors change electrical energy into light, heat, and other kinds of energy. The wire inside a light bulb is a resistor. An insulator is a material that has a lot of resistance. It has so much resistance that it stops the electric current. The plastic covering on a wire is an insulator. Series Circuit In a series circuit, electric current can flow in only one path. If the path has a break, then the current stops. Chapter 1, Lesson 2 Summary Batteries provide energy to some circuits. The energy makes the electric charges move through the circuit. In a series circuit, all of the resistors share the energy. For example, two light bulbs in a circuit shine with the same amount of light. What happens when one light bulb breaks or burns out? The circuit is open. The current cannot flow. None of the bulbs can light. Today most buildings do not use series circuits. Energy Changing Form Resistors change electrical energy into other kinds of energy. Resistors can convert electrical energy into heat, light, or motion. A filament is a very thin coiled wire inside a light bulb. The filament is a resistor. It changes electric current into heat. The filament gets so hot that it glows and gives off light. Producing Heat and Light Every day, you use devices and appliances that need electricity. Computers, televisions, light bulbs, and toasters all use electricity. Some devices change electrical energy into light. They also produce some heat. Other devices convert electricity into heat. They sometimes produce light as well. Intervention Study Guide © Pearson Education, Inc. 4 Charges in Motion Name ______________________________ Lesson 2 Questions Use with pp. 14–19 Lesson 2 Questions 1. What is the difference between an open circuit and a closed circuit? 2. What does an insulator do to electric current? Give an example of an insulator. 3. A resistor changes electrical energy into other forms of energy. In the Lesson 2 Summary, find two forms of energy that resistors can give off. Circle the two forms of energy. © Pearson Education, Inc. 4 4. What is the resistor inside a light bulb? Intervention Study Guide Chapter 1, Lesson 2 Questions