Apr 16 2009
Electroscope is our Word for the Day
It has been a while since I did the ‘word for the day’ and I had a lot of positive comments the last time I did it. Here is what I do – I have a big, fat science book (The Dictionary of Science by Lafferty and Rowe) of fun science stuff – I open the book to any place with out looking and drop my finger on the page, and where my finger rests is the ‘word for the day’!The word chosen by random pointing is Electroscope.
This is an apparatus for detecting an electric charge. The simple gold-leaf electroscope consists of a vertical conducting metal rod ending in a pair of rectangular pieces of gold foil, mounted inside and insulated from the metal case. When an electric charge is applied to the one end of the metal rod, the gold leaves diverge because they each have received a similar positive or negative charge, thus they repel each other.
The polarity of the charge can be found by bringing up another charge of a known polarity (positive or negative) and applying it to the metal rod. A like charge will have no affect on the gold leaves and nothing will occur, a opposite charge will cause the gold leaves to collapse.
This device is a teaching tool used to study the reaction and effects of positive and negative charges. The earliest electroscope was invented around 1600 by physician, William Gilbert and was a pivoted needle apparatus. John Canton invented the Pitch Ball electroscope in 1754 and the one referenced above, the Gold Leaf electroscope was invented by Abraham Bennet in 1787.
Image from www.sparkmuseum.com
Thanks for teaching me a new word.