Demonstration or class experiment?
Physics, more than any other science, can be demonstrated principle after principle by direct and simple experiments. In some cases, it is clear that an experiment should be done either as a demonstration or as a class experiment. But many experiments can be done in either way, each having advantages and disadvantages.
Demonstration experiments can clarify a physical principle or show some interesting application of a principle. Make sure that students in the back row, as well as the front row, can see and hear what is going on. The best demonstration experiments avoid unnecessary detail – students can see and understand the whole working arrangement.
Other reasons for demonstrating experiments include safety reasons, and limited apparatus. Demonstrations can also be used as a part of a revision session or when you want to draw quick comparisons, e.g. looking at the behaviour of water waves and comparing that with light or sound. In a short lesson, there may simply not be time for students to carry out their own investigations, after they have set up and dismantled ripple tanks.
Class experiments give students direct experience of physical phenomena. Just as important, they allow students to practise being scientists: discussing, developing hypotheses, designing experiments, predicting outcomes and returning to fresh hypotheses and more experiments. They develop their powers of observation, thinking and problem-solving. Active learning follows the adage ‘hear and forget, see and remember, do and understand’.
Because some students work more quickly than others do, it is a good idea to give students a series of questions to pursue. With a selection of extra equipment set out cafeteria style, students can then proceed at their own pace. That way all remain engaged and faster students accomplish more.
Through class experiments, students can learn
- how to devise experiments
- how to work on their own
- how to make mistakes
- how to solve practical problems
- how to enjoy success
- and they learn a little theory too.