Transition Year Electronics

1. Circuit Diagrams

A circuit is made up of components (resistors, bulbs, etc.) and a source of electricity (e.g. battery) joined together by conductors (e.g. wires). The electricity has to flow all the way around for the arrangement to work; thatís why it is called a circuit.

To describe a circuit on paper we could try drawing a picture. But this may not work very well; not everyone is good at drawing. And anyway as the circuit gets bigger a picture starts to look very complicated. So instead we draw a diagram. A circuit diagram uses internationally recognized symbols for components. Conductors are shown as straight lines, which meet at right angles.Here are some symbols which you may know:
cell(usually 1.5V)\

 battery (cells joined together)




1. Name the components A, B, C, and D in this diagram:





2. The bulbs in this diagram are connected in parallel:
When the switch S is closed which bulb or bulbs light? _____________________
    If B1 blows, what happens to B2? _____________________
    Explain why it would be a good idea, if a lot of bulbs have to be connected together, to wire them in parallel. Give an example. ____________________________________________________________________________
3. Look at the bulb and switches in this diagram:

When S1 and S2 are both on, which bulb or bulbs light? ______________________________
When S2 is on and S2 is off, which bulb or bulbs light? ______________________________
When S1 is off and S2 is on, which bulb or bulbs light? ______________________________
When S1 is off and S2 is off, which bulb or bulbs light? ______________________________