# Putting the two lines of thinking together(Teaching tip)

### Two lines of thinking converge

The challenge for the pupils here is to recognise the two effects which follow from increasing the number of batteries and lead to the increased brightness of the bulb:

• The bulb is brighter because the current is bigger–more charged particles per second.
• The bulb is brighter because the extra battery shifts more energy for each charge.
• You'll have to decide how to do this most effectively.

We return to thinking about how to draw on the three key elements in sequencing this part of the teaching.

Here our advice is to start with observations and measurements (notice and record what actually happens) and then account for these observations and measurements in terms of the electric circuit model and a teaching model.

### Exploiting the teaching model

This approach is the reverse of that taken in episode 01, where the teaching started with making predictions from the model.

With the approach taken here, the teaching model supports the observations and helps pupils see that they are reasonable.

Teacher: OK, so what can you tell me about the current when a second battery was added?

Teacher: Right, the current was bigger and that the bulb was brighter.

Teacher: Now, can anybody picture what's going on here in terms of the rope model?

Teacher: That's exactly right! I pulled the rope around more quickly and Julia felt her hands being heated up more.

Teacher: Now who can talk through that in terms of charge and energy?

Teacher: Excellent! As the second battery is added, the charged particles move around the circuit more quickly and twice as much energy is shifted by each charge.