Energy & Forces - Properties & uses of energy - Electric circuits - G23 - EF-D1.5

Energy & Forces - Properties & uses of energy - Electric circuits - G20

Teacher's Guide

EF-D1.5

1. Circuits become very complicated once you add in a few more bits and pieces and become almost impossible to draw. Think of the circuit you need to run the lights in your car - with headlights, sidelights, reversing, indicator, brake, parking and fog lights -as you can imagine it becomes like tangled knitting!

To make it easier to draw circuits we use a set of symbols which allow drawings to be clear and usable. Wires are always shown as straight lines with right-angle turns even if in a real circuit they twist and turn.

Some of the other symbols we use are as follows :-

wire	indicator or light source	cell	battery of cells
closed switch	open switch	2-way switch	buzzer
loudspeaker	earphone	motor	bell

The animated circuit shown an example of a series circuit - You can see that the circuit is broken (and the lights go out) as the crocodile clip is removed from the battery. Does it matter which connection (+) or (-) is removed if you want to put the lights out? Which of the components above, if added to the circuit, would make it easier to control the lights?

Some Christmas light sets are connected like this as are the parts of a simple circuit using, say, only one lamp and a switch. In series circuits with lamps, if one bulb fails then all the others go out.

Worksheet D15a (G) gives the children some simple circuits as they appear in reality and asks them to draw them using the symbols given on the sheet.

2. Worksheet D15b (G) gives some simple circuits for the children to put together from circuit diagrams.

3. We are now only asked to teach series circuits but it is important to be aware of parallel circuits in case the children make them by accident! Note however that construction of a parallel circuit is a Level E attainment target - see below.

A circuit with a battery and three bulbs in parallel would be drawn like this :-

Construct a parallel circuit, following diagrams

EF-E1.6

In a series circuit the bulb or buzzers are connected in a line one after the other - just like a series on the TV - one episode follows another.

In a parallel circuit each bulb or buzzer has its own circuit with the battery - the circuits run parallel to each other.

If a bulb blows in the series circuit then the loop going to and from the battery is broken and the other bulb will go out.

If a bulb blows in the parallel circuit then the other bulb will remain lit because its loop is still intact.

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