Rough Guide
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The different types of components we have encountered each have a symbol to represent them in a circuit diagram. A circuit diagram is just a picture of how all the components in a circuit are connected together.

Here are the symbols for the components we have met:

wire wire
join join
resistor resistor
preset preset - the arrow represents the wiper
capacitor non-electrolytic capacitor
electrolytic capacitor electrolytic capacitor - the black line represents the negative plate
led LED - the arrow shows the direction that conventional current can flow (electrons actually flow in the opposite direction!)
transistor transistor - the arrow shows the direction that conventional current flows
piezo piezo speaker (there is no standard symbol for a piezo)
battery battery

Here is a complete circuit diagram. Don't worry about what the circuit does (it just lights up the LED) but notice the fact that you can trace a continuous route from the battery through the resistor and LED and back to the battery, i.e. it is a circuit.




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