🔬 Chapter 3 — Electricity: Circuits and their Components
Class 7 Science | Curiosity | EduGrown Notes
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⚡ Electricity — Circuits and their Components! Powering our world!
⚡ Electric Cell & Battery
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🔋Electric Cell = portable source of electrical energy | Has two terminals: positive (+) and negative (–)
🔋The metal cap = positive (+) terminal | The flat metal disc = negative (–) terminal
⚡Battery = two or more cells connected together | + terminal of one connects to – terminal of next
💡More cells = more energy and longer-lasting power for the circuit
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⚡ Electric circuit components — bulb, wires, cell, switch
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🔋 A simple electrical circuit connected to a bulb
💡 Simple Electric Circuit
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🔄Electric Circuit = closed path through which electric current flows
💡Components of a basic circuit: Cell/Battery, Switch, Electric Bulb (lamp), Connecting Wires
✅Closed Circuit = current flows → lamp GLOWS
❌Open/Broken Circuit = current cannot flow → lamp does NOT glow
🔌The switch opens or closes the circuit — controlling the flow of current
Never perform experiments with home electrical sockets! Use only batteries/cells (like in torchlights) for experiments.
⚡ Conductors & Insulators
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🔌 Conductors allow current to flow through them
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⚡ Insulators block the flow of electric current
✅ Conductors
→Allow electricity to flow through them easily
→Mostly metals: copper, iron, aluminium, gold, silver
→Used for wires, circuits, electrical fittings
❌ Insulators
→Do NOT allow electricity to flow through them
→Rubber, plastic, wood, glass, dry air
→Used as safety covers for wires and handles
📐 Circuit Diagrams & Symbols
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📐Circuit diagrams use standard symbols to represent components — makes it easy to draw and read circuits
🔋Cell = two parallel lines (long thin = +, short thick = –)
💡Bulb = circle with X inside
🔌Switch = gap in wire (open) or completed line (closed)
〰️Wire = straight lines connecting components
💡 Torchlight — A Simple Circuit!
A torchlight has: Cell(s) → Switch → Bulb connected in a loop.
Switch ON = circuit closes → current flows → bulb glows!
Switch OFF = circuit opens → no current → bulb off!
The cells are placed with + terminal of one touching – terminal of next (series connection).
Switch ON = circuit closes → current flows → bulb glows!
Switch OFF = circuit opens → no current → bulb off!
The cells are placed with + terminal of one touching – terminal of next (series connection).
⭐ Quick Summary
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📝 Key Points
🔋Cell = portable electricity source, has + and – terminals | Battery = 2+ cells connected
🔄Circuit: Cell → Switch → Bulb → Wire | Closed circuit = glow | Open circuit = no glow
✅Conductors (metals: copper, iron) = electricity flows | Insulators (rubber, plastic) = no flow
📐Circuit diagrams use standard symbols for cell, bulb, switch, and wire