The experiment sets with many questions

Anrdzej Trzebuniak

Idea of “The experiment sets with many questions” has already been three times presented on this conference in past years. I think that the way of asking questions (through an experiment) should be an essential element of teaching of physics – so, I would like to present the next set of this type of experiments.

Using these sets could be a help for a teacher preparing an interesting revision lesson, and might be good for facultative lessons as well. These sets can vary the work with pupils and can make the understanding and retention of knowledge easier.

In the set, the emphasis is very often placed on the element of surprise, on seeming disagreement with previous pupil’s experience. Therefore, the questions connected with the set are sometimes tricky. Better retention of knowledge (presented phenomenon or process) is the purpose of all these steps.

These factors cause that giving the correct answers should come after thought process based on association of known theoretical facts and their matching to the situation presented in the experiment.

Discussed experiment set, as presented previously, has resulted from preparing The Physics Competition for high schools which has been organized for many years. It is a tradition that the final questions concern experiment sets. These experiments, prepared for Physics Competition, have been named “The experiment sets with many questions”. Idea of the set lies in the possibility of making many logically ordered questions for the presented experiments. The experiments in the set concern the same phenomenon showing its various aspects. Each question concerns properly modified experiment. You should either predict the effect of the experiment or explain observed effect of the experiment.

The experiment set was presented in the same way as on the Physics Competition. Rules of the competition limit number of questions up to four, the limited way of experiment’s description does not disclose the essence of the phenomenon till the last moment.

The task for competitors is to give exhaustive answers for the questions concerning the observed experiment.

The electromagnetic influence

1. A linear conductor is connected to the DC (direct current) power pack. A magnetic needle is placed under the conductor. After the current is switched on, the magnetic needle changes its former position.

The first question (prediction):

How will the magnetic needle act when the AC (alternating current) flows by the conductor? Give reasons.

Answer:

The set is connected to the AC transformer. While the AC is flowing, the magnetic needle doesn’t change its position.

2. Second experiment – Ampere’s experiment. The same DC is flowing through two parallel tapes in the same direction. The tapes are pulling closer.

The second question (prediction):

How will these conductors act when the AC flows through them? Give reasons.

Answer:

Similar as before, the set is connected to the AC transformer. After the current had been switched on, the tapes are also pulling closer.

3. A long electromagnet is DC-powered. Next to the electromagnet, parallel to it, a conducted tape hangs down freely. If DC flows through the tape, the tape will wrap around the electromagnet.

The third question (explanation):

Explain the acting of the tape.

4. Two coils made of identical cord, of the same length and diameter are parallel connected to DC power pack. When the current flows through the coils, we bring closer a magnet with the same pole sided to each one. One of the coils is pushed away from the magnet and the second one is pulled up.

The fourth question (explanation):

Explain the cause of such behavior of the coils.

Using similar “experiment sets with many questions” in school practice, we can ask questions in a different way, change number of questions, modify the experiment sets. If some effects of experiments can be surprising, their attractiveness rises, arousing pupils’ interest and provoking questions.

The stimulation of such pupils’ behaviour is an extremely important factor which brings success in the teaching of physics.