A sequence to develop ideas about simple electrical loops
Classroom Activity for 5-11
Based on the Physics Narrative and the Teaching and Learning Issues
Meeting reality: valuable experiences
Electrical loops are rather pervasive, as they are such a convenient way of getting jobs done. That's because electrical loops are good at powering things, and because that power can be controlled. So it makes some sense to start off by looking at the jobs that electrical loops can do for us in the lived in world, and to move from there to creating and varying loops for themselves.
There is some practical difficulty in investigating mains electricity: not helped by the fact that many mains plugs and sockets have three terminals. Therefore we'd suggest not trying to make too careful a link between these early explorations and later work with making loops. ( There is a clear connection, but it's not simple – you can see more in the SPT: Electricity and energy topic.)
There is however plenty of simple practical activity that can be used to get children off on the right track in thinking about electrical loops. As much of this involves making things there are opportunities for strong links with other parts of the curriculum.
- identify sources of electrical power
- make and vary electrical loops
- choose materials for making electrical loops
A sequence for developing the idea
This is a rather short sequence focusing on electrical loops, once we have established the pervasiveness of electricity.
We think it's very helpful to think in terms of loops, as all electrical circuits are made of loops. Finding the loop, breaking the loop, making the loop and choosing what to put in the loop are all useful activities they get children thinking along the right lines. Each loop needs thinking of as a whole if you are to understand it and that's a further advantage of thinking about electrical circuits in terms of complete loops.
The ideas are developed in the Physics Narrative.
A survey activity, identifying electrical appliances in the everyday world.
Writing: a day without the electrical loop
A story writing activity: imagine a day in which there was no electricity available to power devices, and the consequences.
Tracing out loops in battery-powered devices
Here children can study simple battery-powered objects where they can rather easily notice the electrical loop. They should be encouraged to make a variety of records of what they notice.
Here children make simple electrical loops, taking pleasure in making something simple that works.
Choosing materials for making loops?
Some materials are better for making electrical loops than others: here children can explore what they might use to complete loops.
This activity introduces simple switches, and puts them to use.
Here there are a simple series of challenges: to build circuits to solve problems. In each case the solution is a single electrical loop.
Children are set the task of systematically varying what is in an electrical loop and then making a record of what they notice. You can seek out simple patterns, but full-blooded theorising is not expected.
Messages from research and practice: specific tripwires for this idea
Keep in mind a clear idea of where children's understanding of electric circuits is expected to be at the end of the next step in studying circuits, and not this one. Here you do not have to introduce any reasoning about what happens inside the wires, but it is useful for you to have in mind in order to know what children should be exploring, and in order to avoid seeding unhelpful Ways of thinking about electrical loops.
Helpful and unhelpful ideas about electric circuits
This is a summary of the right tracks down which children can go, and also of the wrong lines which their thinking can follow. In this introductory phenomena
Where do the charges come from?
The battery does provide the active element in an electrical loop, but the wires or other conductors already contain electrical charges free to move. It is possible to introduce batteries in such a way that you get children thinking that everything starts in the battery: this is not true. in particular when you trace out circuits, because the important point is that it is a complete electrical loop, it's helpful to start at different points around the loop – and not always to start the battery.
Electrical loops are made of electrically conducting material – or
conductors. Deciding what is good to put in such a circuit is a matter of choosing a material. However, the distinction between conductors and insulators is not clear-cut.
Each complete electrical loop acts as a whole: you cannot think effectively about each of the parts independently.
Do the charges move instantly?
The resistance sets the current for the whole circuit
What happens in one part of the circuit nearly instantaneously affects what happens in another part of the circuit. It is really unhelpful to argue about electrical circuits as a story-like process, where what happens in one location sets up a message which is carried around in some sense and then later affects what happens in another part of the circuit. This is really misleading thinking.
In the end, you'd like children to appeal to reason confidently about electric circuits. that mean having a good mental model of what is happening in electrical circuits, as opposed to a series of vaguely appreciated analogies.
Thinking fruitfully about circuits
In thinking about conversations that have and explorations to promote, it's really helpful to have in mind a manipulable model that children might be working towards: not that they'll reached that model now, simply that you can set them off on the right path.
Varying what you place in an electrical loop affects everything in the loop: this is therefore complex reasoning, not advised for the majority of children of this age. At this stage these are simply to raise your awareness of issues that will arise in the future, so that you can set children off along the right path.
These challenges and some suggestions for working with them are more fully explained in the Teaching and Learning Issues.
Representing and reasoning: doing physics
Children will be exploring the phenomena associated with electrical loops. They will not be theorising about what happens inside the wires, at least that's not a formal requirement. However, in your discussions with children, it will be useful to have in mind a way of thinking about electrical circuits which can support such discussions.
So most of the physics narrative here is for the benefit of teachers, rather than the benefit of children: it is to provide you with the background support the conversations in the classroom, rather than provide material which might be developed with children in the classroom.
Electric current: a flow of charges
A simple loop: current the same everywhere
When an electrical circuit is complete and functioning there is a flow of charges everywhere in that loop: the charges originate in the loop and set moving by the battery or power supply. Such a flow of charges is called an electrical current.
A simple loop: current the same everywhere
Adding extra elements to the electrical loop (more batteries or more bulbs) affects this flow of charges. adding more batteries increases the flow and adding more bulbs reduces flow, because it increases electrical resistance.
Thinking fruitfully about circuits
A good way of thinking about electrical loops. is to compare them with mechanical loops.
For children, it's all about the phenomena, not the details of what happens inside the wire.
- use physical artefacts, not circuit diagrams
- encourage thinking in loops
Find out more from the Physics Narrative.