# 3 Strengths and limitations of models and analogies

There are some general strengths and limitations to the use of models and analogies, but every model and analogy has its own strengths and limitations.

Simple models may work well in a limited range of situations and a model that is appropriate for one context may be rejected as inadequate in another. Sometimes, there are two or more models you could use in a particular context, each offering a slightly different approach.

Choice of model or analogy is important. If your students are not familiar with an object or situation, you should not use it as part of a model or an analogy, as it could make them more confused.

It is also important to be aware of possible additional misunderstandings created by the models you use. Sometimes, students can be distracted by what you as a teacher regards as irrelevant details, or can misapply some of the details when they recall the model.

For example, you might use a ‘roller coaster’ model of electric circuits to model the need for electrical potential. This shows the idea that the cars need to be dragged up to a high point before they will start to roll on their own, and the idea that all the charge just moves round the circuit with the idea that all the cars just go round the track and nobody gets out during the ride. This should be a suitable model, but it is possible that instead of learning what you intended, your students might fixate on ‘the first hill of a roller coaster is always the highest’ and decide that somehow there is less energy available as you go further round a circuit.

You will only know that misunderstandings have crept in with your model if you ask your students about the model and listen carefully to check their understanding. You can also pick up some issues by asking your students to draw diagrams or add information and comments to diagrams that you have provided. You can find out more about probing your students’ understanding in the unit Probing understanding: work and energy, and in the key resource ‘Assessing progress and performance [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] ’.

## Activity 3: Comparing two role play models of an electric circuit

This activity is to give you experience of using and evaluating physical models with your class. You will need Resource 2 for this activity.

You could introduce and use either of these models at various times during a teaching sequence, but asking students to compare and evaluate models can be particularly useful at the end of a topic, as it can help students to review their understanding.

Before the lesson, identify what groups your students will work in and how you are going to introduce the activity without telling them too much about the two models.

You will need to provide an instruction sheet or a poster, including the questions you want your students to think about, for each model. Each group of students needs to try out both models. Some groups will start with the rope model and other groups, with the ‘sweets’ model. Then you will need to stop everyone so they can swap resources with a group using the other model.

Circulate around the groups as they work. Encourage them to share their ideas with each other. Be prepared for things to get noisier than usual, especially if your students are trying to make themselves heard in large working circles.

When everyone has tried both models, discuss the questions with the whole class.

Ask your students to discuss in their groups what are the strengths and limitations of each model. Discuss these ideas as a whole class.

2 Using models to support learning about electricity