Chapter 3 Electricity Circuits and Their Components Chapter Summary and NCERT Solution 2025

⚡ Electricity: Circuits and Their Components — Summary with NCERT Solution (Class 7 Science)

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Electricity Circuits and their Components (AI Generated Image)

Electricity is one of the most useful forms of energy in our daily lives. It helps in lighting, cooking, communication, transportation, heating, cooling, and entertainment. This chapter explains how electricity flows in a circuit, the main components of a circuit, and the difference between conductors and insulators.

🔋 1. Electric Cell

An electric cell is a small, portable source of electrical energy.
It has two terminals – a positive terminal (+) and a negative terminal (–).
Electric current flows from positive to negative through a circuit.
Cells are used in torches, clocks, and remotes.

🔌 2. Battery

A battery is a group of two or more electric cells connected in a series.
Connecting more cells increases energy output and helps devices run longer.
Batteries are used in mobile phones, toys, cars, and laptops.

💡 3. Electric Lamp and LED

An incandescent lamp has a thin filament that glows when current passes through it.
LEDs (Light Emitting Diodes) glow without a filament and consume less power.
The longer leg of an LED is positive, and the shorter leg is negative.
LED light glows only when connected in the correct direction.

⚙️ 4. Electric Circuit

A circuit is a complete path for electricity to flow.
When the circuit is closed, current flows and the lamp glows.
If the circuit is open, the current stops, and the lamp does not glow.
The flow of current is always from positive to negative terminal.

🔘 5. Electric Switch

A switch controls the circuit by opening or closing it.
ON position: circuit closed, current flows.
OFF position: circuit open, current stops.
Switches are used in torches, fans, lights, and home appliances.

🔲 6. Circuit Diagrams

Circuits can be shown using symbols instead of drawings.

Common symbols:

Cell: |‒|
Battery: multiple cells
Lamp: (⊗)
LED: 🔺 with arrows
Switch: line with gap
Wires: connecting lines

This standard form is called a circuit diagram, used globally for clear understanding.

⚡ 7. Conductors and Insulators

Conductors: materials that allow current to pass easily.

Examples: Copper, Aluminum, Iron, Silver.

Insulators: materials that stop the flow of current.

Examples: Plastic, Rubber, Wood, Glass.

Wires are made of metal (conductor) and covered with plastic (insulator) for safety.

🔄 8. Types of Electric Current

Direct Current (DC): Flows in one direction — from cells or batteries.
Alternating Current (AC): Changes direction — supplied to homes from power plants.
DC powers small devices, while AC powers heavy appliances.

📘 Key Takeaways

Electricity flows only in a closed circuit.
Cells and batteries act as energy sources.
Lamps and LEDs convert electrical energy into light.
Switches control the flow of current.
Conductors carry current; insulators protect us from shocks.
Circuit diagrams use standard symbols for universal understanding.

~~The END~~