Metaphors are used extensively in teaching electronics theory. They range from the 'waves' of radio signals to the 'web' of communications networks, and even further afield.
In this book I discuss these metaphors and their usage. I investigate the effectiveness of the metaphors in conveying the required information and image, and also whether the metaphors have any long-term effect on remembering the required facts.
I show that some people are less receptive of metaphors than others, as might be expected since understanding the relationship of the metaphor to the fact require a degree of imagination. It appears that some people simply do not get the link between the metaphor and the fact. Indeed, I found that some people learn better without the metaphors which tend to confuse them. Some people remember the metaphor long after the fact has become commonplace, whereas others forget the metaphor as soon as it has done its job of explanation.
Since the connection between the metaphor and the fact is sometimes tenuous and can even be misleading if taken too far, it seems that forgetting the metaphor has a useful function as it removes the risk of over-interpretation and association.
The use of metaphors in teaching electronics theory has a useful function in aiding most students' learning. However, it can be taken too far, become confusing to some students and may reduce the ability of some of them to understand the theory.
Metaphors should be used with care in teaching electronics theory and the students' responses to them monitored for effectiveness or problems.
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Metaphors are widely used in electronics, often using water as a parallel: electricity 'flows'; signals radiate in 'waves'. In this chapter I discuss three metaphors used in teaching electronics theory. The first - in which electricity is compared to water in a pipe - is used by almost all teachers, and appears in almost every text book, often with pictures (For example, see Phillips 1993). The other two are less common, but still widely used. They are examples of the type of metaphors used in illustrating the principles of electrical and radio theory.
Following the descriptions, I discuss some of the problems which might arise in using the metaphors, in particular I show where the analogy breaks down. In some cases probing beyond the immediate similarity can produce contradictions and hence confusion in the mind of the learner. Some problems suggested and discussed by other researchers in this area form part of the next chapter.
In learning basic electrical theory, students are encouraged to think of an analogy with water. The amount of water flowing through a pipe is presented as a comparison with current flowing through a wire. Water flows at a rate depending on the pressure applied by a pump of some sort, just as electricity flows at a rate depending on the electro-motive force provided by a battery or generator. Special devices can be used to measure these quantities - flow and pressure meters - the main difference being that water meters are usually mechanical whereas electricity meters are themselves electrical devices.
The metaphor can be carried further. If a pipe breaks then the water no longer reaches the point where it is to be used; a broken wire will stop electricity from reaching the appliance plugged into the socket. So, in both cases, a complete circuit is required for useful work to be done.
Taps are used to control the flow of water, reducing the flow and pressure by an amount to suit the work to be done. Electric switches are a little bit different in that they are either on or off: they can stop or allow the flow but not change its rate. Perhaps a better comparison to the water tap is the type of dimmer control often used on lights, where the brightness can be adjusted from off to full on, or any point in between. However, the basic idea of control of the rate of flow still holds.
When water meets a division in the pipes, the flow divides up in a proportion which depends on the nature of the pipes. More water flows down a bigger diameter pipe than a small one, since there is less restriction and resistance. Similarly, electric current flow divides at a wiring junction, and the amount of current in each branch is inversely proportional to the opposition, or resistance, in that branch. Thicker wires can carry higher currents because their resistance is lower. Lower resistance means less loss of energy in overcoming it, and hence less heating effect.
Metaphors, such as taps and running water, thus provide a step from what may be taken as common knowledge for most people (at least in places where there are taps and running water) and used to introduce the new concepts associated with electricity.