Circuits and their Components

Overview

An electric circuit is a path through which electric current flows. This chapter explains cells, switches, bulbs and wires, and how they combine to make working circuits.

Key concepts

• A cell provides the energy to push current through a circuit.
• Current flows only in a closed circuit; an open circuit stops it.
• A switch opens or closes a circuit.
• Conductors allow current to pass; insulators do not.
• Symbols are used to draw circuit diagrams.

Important terms / formulae

• Electric current: flow of charge through a conductor.
• Cell / battery: source of electrical energy.
• Conductor: material that lets current flow (e.g. copper).
• Insulator: material that blocks current (e.g. rubber).

Solved example or key process

1. Connect a cell, a bulb and wires in a loop.
2. Add a switch in the path.
3. Close the switch: the circuit is complete and the bulb glows.
4. Open the switch: the circuit breaks and the bulb goes off.

Important questions

1. What is the difference between an open and a closed circuit?
2. Give two examples each of conductors and insulators.
3. What is the function of a switch?
4. Draw the symbol for a cell and a bulb.

Quick revision

A circuit needs a source (cell), a path (wires) and a device (bulb). Current flows only when the circuit is closed. Conductors allow current; insulators block it.