In a Year 4 class, Paul confidently made a circuit and explained that positive power from the battery travelled along the wire to the bulb. On lighting the bulb the positive power was turned into negative power which returned along the second wire to the battery. Once all the positive power had been replaced by negative power, the battery would be flat. In the same class, Susanne explained that she needed two wires in her circuit because "not enough electricity can get along one wire to make the bulb light up" Personal experience of making and observing working circuits, together with knowledge from everyday life have led both Paul and Susanne to understand that a component separated from the battery needs to be connected to it by two wires, that the battery supplies something needed to make the bulb light and that this something travels through the wires and is in limited supply. These ideas are not inconsistent with a scientific understanding.
However, Susanne may think that the "something" she calls electricity travels along both wires from the battery to the bulb, an idea not in keeping with the science view. This thinking might be challenged by further practical investigation. For example, if she believes that the second wire merely provides more space for the electricity to travel through, then a single, thicker wire might be tried, or two wires both connected to one terminal of the battery.
Such activities might help Susanne to refine her ideas about the physical nature of circuits but she will still be left to imagine for herself what is "going on" inside the wires. Paul, having grasped the notion of a circular pathway, and noticed the + and - signs on the battery has developed an explanation based on a change in the "power" as it travels around the circuit. This allows him to explain a fact with which he is very familiar - batteries go flat.
It is difficult to think of any investigative work which would help Paul towards a more scientific understanding. In further work with circuits he is likely to use and develop his existing model. It is not empirical evidence he needs but a new way to think about a familiar event.
Research has shown that it is not just in the context of electricity that children do not come to a scientific view through their own experience and enquiry; children frequently develop ideas that differ from the ideas of science. This is hardly surprising. Children are unlikely to stumble upon abstract scientific notions such as pressure or energy fortuitously, although they may use the words in an everyday sense. Rather, scientific ideas need to be introduced as helpful ways to think about something.
Many of the activities with which children are involved in the primary school provide opportunities to observe, explore and investigate and develop practical skills. Few of these activities are specifically designed to introduce new ideas in ways which young children can understand and use. Indeed, some primary teachers may be concerned about the appropriateness of teaching concepts they cannot directly show to their class.
However, children like Paul and Susanne already use abstract notions such as "power" in explanations of their observations. If, as teachers, we want to guide the development of children's conceptual understanding in a structured way, rather than leaving it to chance, we need to be able to identify both what children understand already and those new ideas which would be helpful to them. The challenge then is to find stimulating ways to introduce these ideas.
Starting to develop a scientific explanation for the behaviour of circuits involves differentiating a generalised notion of "electricity" into two components, energy and current. The idea of the battery as a source of energy which can be supplied to the bulb where it heats the filament and produces light fits well with many children's intuitive "source-consumer" ideas about how a circuit works and neither Paul nor Susanne should have difficulty with it. The problem then becomes to explain why one wire is not sufficient.
Here the idea of current as a carrier of energy is one which can be helpful to children. They are unlikely to "discover" or develop this idea for themselves through practical experience of circuits alone, because what "goes on" in the wires needs to be imagined. The teacher therefore needs to encourage children to think in a new way and provide opportunities for the ideas to be discussed and used to explain observations.
Many people think about electricity in terms of something else - water flowing through pipes or traffic moving along roads. For children, such analogies may be almost as unfamiliar as the current and energy they are trying to imagine, and representations which relate more closely to children's experience are needed. Teachers and students in the Leeds area have recently been trying out some alternatives: o Children are asked to set up model railway tracks (wires) so that the train (current) can load goods (energy) at the station (battery), deliver them to the factory (bulb) and return to the station without going backwards.
o A child, the "Smartie monster", jumps every time she receives energy in the form of a Smartie to be eaten. Paper cups circulate continuously (current) between the Smartie-supplier (battery), who adds a Smartie to each empty cup returned to her, and the monster (bulb), via an unbroken circle of children (wires).
o A small group of children sit, with the teacher, in a circle, supporting a continuous loop of string in the joint between thumb and first finger. The teacher, (battery) causes the string to move. The children's hands act as the wires providing the pathway for the string (current) to flow along. If one child grips the string slightly more tightly, representing a bulb, but the "battery" stays unchanged, the string moves more slowly and the person gripping the string feels their hand get hot (energy transfer).
Each of these models or analogies has helped children think about electric circuits. But understanding cannot be guaranteed; children need support in using any analogy to aid their thinking. The relationship between the parts of the analogy and what is to be explained, in this case a simple circuit, must be made explicit if they are to make scientific sense of their experiences.
Hilary Asoko is a lecturer in primary education at the University of Leeds