Those who use cameras or camcorders in teaching physics may be directed
to an article "Investigating Coulomb's Law" which appeared in the
January 1998 issue of The Science Teacher (vol 61, #1, pages 46 to 49).
It describes qualitative prelab activities (invented by Bruce Sherwood)
with sticky tapes and quantitative activities (invented by the authors)
with a digital camera or a camcorder. The force between a suspended and
a stationary pith ball is measured as a function of the distance which
which separates them, and as a function of the product of two charges
(arbitrary units). This is possible, even on a summer day, becasue
measurements are made very rapidly (several seconds) to prevent natural
discharging.
Ludwik Kowalski
P.S.
1) The same issue of TSC has an article on teaching thermodynamics
(content organization) in a new h.s. curriculum in Chile.
2) Do you remember a message in which benefits of radiations (in low
doses) was mentioned here several weeks ago? References backing this
claim are given by Joseph J. Devaney (in a letter to the editor of
Physics Today (last issue, page 87).