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Re: Flash & RC circuits

I would suggest that EVERYBODY go to the local one-hour photo shop
and ask for a 'few' discarded flash disposable cameras. These cameras are
'recycled' but I find the photo-shop folks quite willing to pass them on to
interested science type people.

Each unit uses a single AA cell to charge a hefty capacitor. The camera is
easy to disassemble and the circuit is fairly straightforward. Just be
careful NOT to get shocked by the high voltage capacitor. (~ 300 volts) We
have evidence at our school that a direct shock is not fatal, but it does
NOT feel good.

I don't see how the damage that the photo teacher described could happen
with these cheapo flash units, but the expensive ones may well have more
delicate electronics that can get fried.


<From mwilson@colosys.net>

In class a question about the electronic flash attachments used in
photography was voiced.

Apparently the photography teacher warned students that charging
the flash unit, then removing the battery, and then using the flash
would cause extensive damage to the flash unit or battery.

I had just explained how flash units use an RC circuit for the flash,
so failure to let the capacitor reach full charge would damage the
battery.

It does not seem to me removing the battery from a charged circuit
could cause damage (which is how we do the tau experiment in
class).

Am I wrong?

Obviously I told the involved students it could be a rather expensive
lesson to ignore their photography teacher, and it is never smart to
ignor teachers. Of course, being teenagers, they have already tried
all of the warnings on their own.



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Chuck Britton Education is what is left when
britton@odie.ncssm.edu you have forgotten everything
North Carolina School of Science & Math you learned in school.
(919) 286-3366 x224 Albert Einstein, 1936