Experiences

Introduction to electrostatics

Paola Falsini

Italy

High Secondary School

Physics

Teaching in class, Laboratory

Direct

Objectives:
- to provide further examples of forces (in addition to the gravity, friction, elastic force…) in order to strengthen the concept of force as interaction between two objects;
- to learn not only the results of science, but also something about to do science; in order to reach this goal it needs to approach electric phenomenon as result of experimental course in spite of a simple list of notions. It is also relevant to underline that this process was historically very complex and demanding. It is possible to replicate (even if partially) the historical steps with the students through in class and at home activities. This method leads to answer to question like “how can we know that…?”;
- to provide some examples of operational definition (e.g. an object is defined electrified if it is able to attract other objects lighter than itself).
Through home experiments (providing a guide sheet), repeated in the school lab, on objects made electric by wrinkling, on adhesive tapes torn off from a same surface or one another, students understood, for instance, that:
- the final knowledge about the existence of only two kinds of electric charges comes from the repetition of experience among two centuries (we observed that there are no other cases: an object electrified is repelled either by the electrified glass or the electrified plastic);
- the visible attraction or repulsion is mutual even if only one of the two objects seems effectively to be subjected to the force (students observed that an electrified scotch-tape can attract light objects but it is attracted by the hand).
This method is also important because gives the opportunity to understand the name “charge” and its adjectives “positive” and “negative” (like every scientific terminology) have an historical origin. In particular, the electron is conventionally considered negative because of the Franklin’s hypothesis that the glass acquired electric fluid and the amber lost it (on the contrary nowadays we know that the glass loses something and the amber gets it).
The students, thanks to this approach which raised their interest and curiosity, reached good marks in the tests.