It is a simple and an early scientific instrument that is used to detect the presence and magnitude of electric charge on a body.
Who invented the electroscope?
The first electroscope was invented by British physician William Gilbert around 1600.
What does it look like?
Below is a diagram of a gold leaf electroscope.
It consists of a glass container with a metal rod inside it. This rod has 2 thin pieces of gold foil attached to it. The other end of the metal rod has a metal plate attached to it outside the glass container.
How does it work?
- When a charged object, like the positively charged rod, is brought close the neutral metal plate of the electroscope, it causes negative charge in the gold foil, metal rod, and metal plate, to be attracted to the positive rod.
- The plate becomes negatively charged and leaves a positive charge on the gold foil. This is called inducing a charge on the metal plate.
- The induced positive charge on the gold leaves forces them to move apart since like charges repel. This is how we can tell that the rod is charged.
- If the rod is now moved away from the metal plate, the charge in the electroscope will spread itself out evenly again and the leaves will fall down because there will no longer be an induced charge on them.
THINK ABOUT WHAT HAPPENS WHEN A NEGATIVELY CHARGED OBJECT IS BROUGHT CLOSE TO THE PLATE?
