Electric Circuits Basics: quick revision, 18 bites

What a Switch Does

A switch completes or breaks a circuit.

A **switch** is a simple device that either **completes** or **breaks** a circuit. When it completes the circuit, current flows and the device works. When it breaks the circuit, current stops flowing.

Takeaway. A switch controls current flow by closing or opening a circuit.

Making a Simple Switch

Build your own switch with pins and cardboard.

Takeaway. A homemade switch uses a movable conductor to open or close a gap.

ON Position Explained

Closed circuit means current flows.

When the safety pin touches both drawing pins, it **closes the gap** and completes the path. This is the **ON position**. The circuit is **closed**, and current flows from the cell's positive to negative terminal, making the lamp glow.

Takeaway. ON = closed circuit = current flows = device works.

OFF Position Explained

Open circuit stops the current.

When the safety pin does **not** touch the second drawing pin, there is a **gap** in the circuit. This is the **OFF position**. The circuit is **open**, current cannot flow, and the lamp does not glow.

Takeaway. OFF = open circuit = no current = device off.

Switch Placement

Switches work anywhere in a circuit.

A switch can be placed **anywhere** in a circuit. The switches used for lights and other devices at home work the same way, though they are designed differently.

Takeaway. Switch position in a circuit doesn't change its function.

Why Circuit Diagrams?

Symbols make circuits easier to draw.

**Circuit diagrams** use symbols to represent electrical components. This makes it simpler to draw and understand circuits without drawing detailed pictures of each component.

Takeaway. Symbols simplify circuit representation.

Electric Cell Symbol

Long line positive, short line negative.

In the symbol for an **electric cell**, the **long line** represents the **positive terminal**, while the **short line** represents the **negative terminal**.

Takeaway. Cell symbol: long line = positive, short line = negative.

Component Symbols Overview

Know the standard circuit symbols.

Takeaway. Each component has a unique standard symbol.

ON vs OFF Switch Symbols

Closed vs open in diagrams.

Takeaway. ON symbol = connected; OFF symbol = gap.

Home Switches Work the Same

Same principle, different design.

The switches used for **lights and other devices at home** work the same way as the simple switch you built — they complete or break the circuit. They are just designed differently for safety and convenience.

Takeaway. Home switches use the same open/close circuit principle.

Confusing ON and OFF

ON means closed, not open.

Takeaway. Remember: ON = closed = current flows.

Drawing Cell Symbols

Long line is always positive.

In exams, remember: **long line = positive (+)** and **short line = negative (−)** for the electric cell symbol. This is a frequently tested detail.

Takeaway. Cell symbol: long line positive, short line negative.

Remembering Switch Positions

Closed = ON, Open = OFF.

Think: **C**losed = **C**urrent flows = **ON**. **O**pen = **O**ff. The letter 'C' in closed reminds you of 'current' flowing.

Takeaway. Closed = current = ON; Open = off.

Switch in Any Position

Placement doesn't matter.

A switch can be placed **anywhere** in a circuit and still work the same way. Whether near the cell or near the lamp, it controls the entire circuit.

Takeaway. Switch location doesn't affect its function.

Testing Your Switch

Test with a cell and lamp.

Takeaway. Testing confirms: ON = glow, OFF = no glow.

Current Direction

Current flows positive to negative.

When the circuit is closed, current flows from the cell's **positive terminal** to the **negative terminal**, making the lamp glow.

Takeaway. Current flows from positive to negative in the circuit.

Switch as a Bridge

A bridge lets you cross or not.

Think of a switch like a **drawbridge**. When the bridge is down (ON), people can cross (current flows). When the bridge is up (OFF), no one can cross (no current).

Takeaway. Switch = drawbridge: down = ON, up = OFF.

Drawing Circuit Diagrams

Use symbols, not pictures.

Always use **standard symbols** when drawing circuit diagrams. This makes your diagrams clear, universally understood, and easier to grade.

Takeaway. Always use standard symbols in circuit diagrams.