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Electric Circuits — Reading Comprehension

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MS-PS2-3

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This middle school science passage explores electric circuits in depth, aligning with NGSS standard MS-PS2-3. Students will learn how a circuit is a closed loop that enables current to flow, and how essential components like power sources, wires, loads, and switches interact. The passage explains the difference between open and closed circuits and introduces basic circuit diagram symbols, providing real-life examples such as flashlights and lamps. Activities include comprehension questions, writing prompts, and graphic organizers that encourage analytical thinking and application of concepts. Spanish translations and simplified versions are included for accessibility. Audio integration is available for diverse learners. This passage is ideal for grade 6-8 students studying physical science, systems, and the role of electricity in technology and society.

CONTENT PREVIEW

Electric-circuits-4 — Example circuit diagram using standard symbols

Electric circuits are the foundation of almost every technological device that uses electricity. When you turn on a light or use a computer, you are using a system made up of several parts working together. Each part of a circuit plays a specific role, and understanding these interactions helps explain why devices work—or why they sometimes fail. The study of circuits is essential for understanding how we power homes, schools, and modern society.

How Circuits Work: Closed Loops and Flow
A circuit is a closed loop that allows electric current—the flow of tiny charged particles called electrons—to move continuously. For a circuit to function, it needs a power source (such as a battery or electrical outlet), conducting wires to carry the current, a load (like a light bulb or motor), and often a switch to control when the circuit is open or closed. When the switch is closed, the path is complete, and current flows from the power source, through the wires, into the load, and back to the source. If any part of the loop is broken (an open circuit), current cannot flow, and the device will not work. Circuit diagrams use symbols to represent these components, making it easier to design and troubleshoot electrical systems.

Applications and Variations: Everyday Circuits
In a flashlight, a simple electric circuit includes a battery (power source), metal wires, a small bulb (load), and a switch. When you press the switch, the circuit closes and the bulb lights up. In a lamp plugged into a wall outlet, the principle is the same, but the power source is the electrical grid instead of a battery. Engineers use circuit diagrams to map out these systems. A key measurement in circuits is voltage, which is the force that pushes current through the circuit, and resistance, which limits how much current can flow. For example, the resistance of a light bulb's filament determines how bright the bulb will be at a given voltage.

Open vs. Closed Circuits and System Behavior
Open circuits occur when the loop is broken—by a switch, a loose wire, or a burnt-out bulb. In this state, the current cannot complete its path, so the device turns off. Closed circuits, on the other hand, allow current to flow smoothly. Some devices, like safety switches, are designed to create an open circuit to prevent overheating or danger. Understanding the difference between open and closed circuits helps us diagnose problems and build safer devices. The relationship between voltage, resistance, and current in circuits is described by Ohm’s Law, a principle that helps engineers design efficient electrical systems.

Electric circuits are essential to technology, from powering simple toys to running entire cities. By mastering how circuits operate, we connect scientific principles to real-world innovations in transportation, communication, medicine, and more.

Interesting Fact:
The world’s longest electric circuit is the global power grid, which connects millions of homes and businesses across continents!

What is the main function of a switch in an electric circuit?

To open or close the circuitTo provide energyTo use electricityTo measure voltage

Which component supplies energy to a circuit?

LoadPower sourceSwitchConducting wires

What happens in a circuit when the loop is broken?

Current flows fasterThe device turns offVoltage increasesThe load uses more energy

In a flashlight, which part is the load?

BatteryWiresBulbSwitch

What is a circuit diagram?

A drawing using symbols to show circuit partsA measurement of currentThe amount of resistance in a wireA type of battery

What does resistance do in an electric circuit?

It pushes current through the circuitIt limits the flow of currentIt opens the circuitIt measures voltage