# 2 Using models to support learning about electricity

Teachers use a range of models and analogies to help students to develop their knowledge and understanding of science concepts.

Models and analogies relate unfamiliar concepts and experiences to familiar, everyday ones. For example, an analogy often used to explain electric circuits is: ‘electric current in a conductor is like water flowing in a river or a pipe’.

Physical models use tangible, real objects to represent parts of an object or system (Figure 1). Students manipulate real objects to describe and explore concepts, processes and relationships. For example, you might model the effect of changing potential difference across an electrical circuit by tilting a track with marbles on it: the marbles don’t roll if the track is flat, but will roll from high to low if it is tilted. (The marbles are the current and the tilt is the potential difference.) If there is no potential difference, then no current will flow round the circuit. But if you increase the potential difference, the current will increase.

Figure 1 A group of students designing their own physical models. The pencil case with a zip represents a variable resistor.

Physical models can include computer simulations, as well as the use of students themselves as part of the model. For example, students might take part in a role play activity where one person is the battery and pulls a loop of rope around; as it is supported by the group; the moving rope represents moving charge in the circuit. There are many computer simulations available on the internet. You could encourage your students to go to an internet cafe and find some.

A key point about using any model with your students is that it should be an interactive process. You should not simply tell your students what the model is: you should ask questions such as ‘What does this feature of the model represent?’ or ‘What represents resistance in this model?’, and encourage your students to explain their ideas. They will learn more if they have to identify the connections rather than simply being told.

Your students should also work in groups and discuss their ideas with each other. Using the model and talking about it should help your students to develop their understanding, and when you listen to your students’ comments and discussions it will help you to have a better understanding of where they have difficulties.

## Case Study 2: Role play model for electric circuits

Mr Patel attended a training session at the local DIET and experienced the use of a role play model for electric circuits.(You can find descriptions of both these models in Resource 2.)

Last week I attended a training session about teaching electricity. I was surprised at first when the trainer told us that we were going to try out a model for electricity called ‘the rope model’. I had not met this model beforeand was even more surprised when I found out that it was a role play activity! I went back to school and tried it with Class X.

There were 50 students in Class X so I divided them into two groups of 12 and two groups of 13. Each group had a circle of washing line. I told them to hold it loosely in their hands. One person pulled it round.

Then I quietly spoke to one person in each group and asked them to hold the rope a bit more tightly. It became harder for the person pulling the rope to make it move, and the person holding the rope tightly found that their hands got warm.

I wrote some questions on the blackboard:

• What does the person pulling the rope represent in this model?
• What does the moving rope represent?
• What happens when someone holds the rope more tightly? What does this represent?
• How does this model represent electricity flowing in a circuit?

I asked my students to work in groups of four to answer the questions. Whilst they were working, I walked around and listened to the conversations.

After ten minutes, I asked representatives from some of the groups to explain their answers.

Finally, I asked them to get back into their groups of 12 and we did the exercise again. This time, while they were moving the rope, I went through the answers to the questions to highlight the key features of the model.

The good thing about this model is that all the rope starts moving at the same time. All the charge in a circuit starts moving at the same time, too. This was the point so many students had found difficult to understand when I taught Class X electricity last year. I realised that it was because they were still thinking about charge coming out of the battery and whizzing round the circuit instead of being there all the time and just starting to move when a potential difference was applied.

When someone gripped the rope more tightly, this was the equivalent to adding a resistor. Students could see that the rope was still in the circuit, so the charge wasn’t leaving the circuit, as some of them had thought. Instead some of the energy was leaving through the resistor, because the student acting as the resistor’s hands got hotter.

The whole exercise only took about 20 minutes but I am sure it has helped my students to understand electric circuits better.

 Pause for thought What analogies have you used to teach about electricity? Which ones have worked well?Have you used any physical models to teach about electricity? What were they?

 Video: Storytelling, songs, role play and drama

## Activity 2: Utilising models

You will need the table you completed for Activity 1. Add another column to the right of the table, as shown in Table 3.

Look through the chapter again and identify what models and analogies are used in the text.

Add any other models or analogies that you think might be helpful.

The first row is filled in as an example. You can find out more about the rope model and also about another model called the ‘sweets and cups’ model in Resource 3.

When you have completed the table, compare your notes with those in Resource 4.

Table 3 Considering what models and analogies can help with textbook learning.
SectionActivityKey teaching points/What do I want students to learn from activity and related text?Sources of difficulty?What models or analogies are being used or might help here?
12.1

Current (measured in amperes) is the flow of charge (measured in coulombs) per second

Current measured by an ammeter. Conventional current flow is from + to –

Current and electron drift through a conductor. Current is instantaneous but drift speed is about 1mm s–1

Charge not something that is visible

Confusion over electron flow direction and conventional current

Reconciling slow drift of electrons with instantaneous current

Being used: Electric current as a flow. Circuit is a continuous closed path – any break stops the flow

Might also help: Rope model.

12.2
12.3
12.412.1
12.2
12.3
12.512.4
12.6.112.5
12.6.212.6
12.7
12.7.1
12.8

1 What do students find difficult about electricity?

3 Strengths and limitations of models and analogies