The Electroscope (T2) Flashcards
What is an electroscope and how did it come about?
It is an instrument for detecting electric charge. It was invented by Jean Antoine Nollet (1700-1770)
Briefly explain how an electroscope works..
A metal plate rests at the top of a metal rod, which leads inside the instrument, but is insulated from the rest of the apparatus.
The metal rod has a very thin sheet of metal (usually gold) called a ‘leaf’ attached to it.
If an electrically charged object is brought close to the plate at the top, the leaf moves.
Why is the leaf on an electroscope usually made of gold?
Gold can be beaten into extremely thin sheets.
Explain in detail how an electroscope can be used to investigate charges on different objects..
Charge the electroscope by bringing a positively charged rod close to it.
This attracts negative charges towards the metal plate, leaving a positive charge on the metal road and the gold leaf.
The like charges repel so the leaf rises.
If you touch the top of the electroscope briefly, negative charges are attracted to it from the earth. The electrons move from the earth, through your fingertips and onto the electroscope.
If you then remove your finger and take the charged rod away, the gold leaf is still deflected because the electroscope now has an overall negative charge.
Now if you bring a positively charged object close to the electroscope it will attract some of the negative charges from the leaf so there will be less repulsion from the leaf and it will fall.
If you hold a negative object close to the plate it will repel more negative charges from the plate into the leaf and the leaf will rise even further.
