SECTION ONE: INTRODUCTION FOR WORKSHOP LEADERS

It is common for physics and physical science teachers to avoid the subject of magnetism because they are not comfortable with it. There are at least two obstacles that contribute to this discomfort. The first is that much of the magnetic phenomena that can be investigated in a school laboratory is counter-intuitive. In particular, action-at-a-distance effects and forces are often produced in unexpected directions. Given time, a teacher could produce experiments that would help students around this first obstacle if it wasn’t for the perceived dangers of such experiments. This is the second obstacle. The study of magnetism can, but need not, involve the use of dangerous amounts of electrical energy.

Fortunately, neither of these obstacles is difficult to overcome. Since the counter-intuitive aspects of magnetism do not involve effects frequently observed by students, most student preconceptions are not as firmly held as are those in mechanics. Those preconceptions that do exist can usually be clearly contrasted with the results of experiments which often are so different from expectations that students welcome alternative models and explanations. The second obstacle, the dangers in the use of electricity, can be completely avoided by the use of batteries and the construction of simple pieces of equipment that require little use of energy.

The demonstrations and experiments described in this book have been developed over many years. They involve cheap and simple materials that are commonly available and easy to put together. As much as possible, construction should be done by the students, but its always a good idea to build your own version so that you have a feeling for any difficulties students might have.

The workshop and teaching approach that is suggested is based on my personal observations and research concerning the decisive role that expectations have on our perceptions. Students and workshop participants should often be asked to think about, and preferably put into writing, what they expect to happen before they do an experiment or a demonstration. This approach is becoming more common, but I believe that it does not go far enough. To complete the process students should be asked to suggest alternatives to their expectations.¹ This is based on the observation that when a person has a strong expectation of a result, he or she is likely to see this result or one very similar to it even when it does not occur! On the other hand when expectations are made more general by the consideration of alternatives, it becomes more likely that the observer will accurately perceive the effects. Another aspect of this approach is that the first investigations should be qualitative rather than quantitative. Then, as the student has more experience with the phenomena, it becomes appropriate to ask for more detailed, therefore quantitative, hypotheses, and at this level the teacher should be prepared to advance some of these detailed hypotheses or to assist students in refining their own. Hypotheses that might be suggested to students will appear with the workshop activities.

I. Tell the participants that it is important that students express their hypotheses and consider alternate hypotheses before doing experiments. Brainstorming is an effective way to do this.

II. Time permitting, cover the following Laboratory Activities. Note that the introduction to the set is in the first activity. This is useful for students, but the activity is probably too elementary to cover with teachers in your workshop.

LABORATORY ACTIVITY 2: Seeing Magnetic Fields

This can be done along with Demonstrations and Displays #6 (A Two Dimensional Magnetic Field Viewer) and #3 (A Three Dimensional Magnetic Field Viewer).

LABORATORY ACTIVITY 3: How are Magnetic Fields Produced?

If you are emphasizing qualitative activities, you may want to present only the first part.

LABORATORY ACTIVITY 4: Penetration of Magnetic Fields through Matter

Due to time limitations in a workshop, ask participants to try some of this while doing the previous two activities.

LABORATORY ACTIVITY 5: Electromagnets

LABORATORY ACTIVITY 7: Magnetic Forces on Current Carrying Wires

LABORATORY ACTIVITY 8: Magnetic Forces on Moving Charges

LABORATORY ACTIVITY 11: A Model of Magnetic Domains

LABORATORY ACTIVITY 12: Long Range Repulsion, Short Range Attraction

III. Set up any of the DEMONSTRATIONS AND DISPLAYS that you have materials for. These can be viewed as participants arrive and at lunch time.

IV. You may want to demonstrate PHYSICS CONTEST EVENT #2 (Magnetic Push).