Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Copyright © Houghton Mifflin Harcourt Publishing Company

It’s Shocking! Electricity cannot move through all materials. Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? It’s Shocking! Electricity cannot move through all materials. Insulators are materials that do not allow electricity to flow. Rubber and plastic are examples of insulators. Conductors are materials that allow electricity to flow easily. Metals and some liquids are examples of conductors. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? It’s Shocking! Electric devices need electricity to work. Electric cords carry electricity to the devices. An electric cord contains metal wire. The wire conducts electricity through the cord. Electric cords are wrapped in plastic or rubber. These insulators make the cords safe to handle. Copyright © Houghton Mifflin Harcourt Publishing Company

A Path to Follow Electricity must flow in a closed loop. Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? A Path to Follow Electricity must flow in a closed loop. A path that electric charges can flow through is called an electric circuit. A closed circuit is a complete loop. Electricity can flow through a closed circuit. An open circuit is an incomplete path. Electricity cannot flow through an open circuit. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? A Path to Follow A switch controls the flow of charges by opening and closing the circuit. When the switch in a circuit is open, the circuit isn’t complete. Electric charges cannot flow. When the switch is closed, electric charges can flow through the circuit. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Who Needs a Map? In a series circuit, electric charges must follow only one path. If any part of a series circuit breaks, the circuit is open. Electric charges cannot flow. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Who Needs a Map? Trace the path electric charges follow in this series circuit. What would happen if one of the lightbulbs burned out? Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Who Needs a Map? In a parallel circuit, electric charges can follow more than one path. If any part of a parallel circuit breaks, the charges can still flow along the other parts. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Who Needs a Map? Trace the path electric charges follow in this parallel circuit. What would happen if one of the lightbulbs burned out? Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Circuit Overload! When electric charges flow through conductors, the conductors get hot. If too much charge flows, the conductor can overheat and start a fire. Circuits in homes and buildings have fuses and circuit breakers to protect against fires. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Circuit Overload! Fuses and circuit breakers are switches. They open automatically if too much charge flows through them. When they open, they stop a charge from flowing through the circuit. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 10 Lesson 4 What Are Electric Circuits, Conductors, and Insulators? Circuit Overload! A circuit can overload if too many devices are plugged into it. Each device needs a certain flow of electrical charge, or current. Current is measured in amperes, or amps (A). If too many amps flow through a circuit, the circuit breaker or fuse opens. Copyright © Houghton Mifflin Harcourt Publishing Company