Message-Id: <v01540b0eaf44a3cde80d@[192.174.2.173]>
Date: Thu, 6 Mar 1997 08:40:53 -0800
To: pinhole@exploratorium.edu
From: pauld@exploratorium.edu (Paul Doherty)
Subject: re more electricity
Hi Doug
I'd love the details of the magnetism detector.
We take a clear plastic cylinder, 6 inches long, wrap a hundred turns
around the middle.
Place a neodymium cylinder in the middle (although it also works with
cylindrical fridge magnets.
Attach the leads to an LED.
Then as the magnet is shaken back and forth the LED blinks.
(Developed by Curt Gabrielson)
The secret to making positive charges is to use a plastic bread wrapper,
polyethylene.
Many things that acquire a negative charge when rubbed with wool acquire a
positive charge when rubbed with a bread wrapper. Try PVC and other
plastics.
Its neat to show that when rubbed with wool plastic becomes negative and
when rubbed with a bread bag it becomes positive. This leads to the idea of
charge transfer and the triboelectric series, not to the idea that plastic
is always negative.
There is a circuit in an old DScience Teacher magazine that uses one FET
transistor to detect positive and negative electric charges and to light
red and green LEDs are you interested in seeing it?
Paul Doherty