Chapter 20.2, Problem 21SSC

To determine

To explain:The charging of an electroscope positively using a positively charged rod and negatively charged rod.

Explanation of Solution

Introduction:

Electroscope is a scientific instrument used in old days to detect the existence of electric charge in an object. Electroscope finds electric charge in an object by its movement which is due to the electrostatic force on it. The quantity of charge in a test object is proportional to the voltage of an electroscope. But it gives only a rough idea about the amount of charge in an object.

Charging an electroscope positively using a positive rod:

If the positive rod is kept closer to the electroscope in such a way that it touches the electroscope, then the negative charges from an electroscope will move to the rod and the electroscope becomes positively charged.

Charging an electroscope positively using a negative rod:

The negative rod should be placed closer to the electroscope in such a way that it will not touch electroscopebut touch the electroscope by finger. Then the electrons which are repelled off by the electroscope due to the presence of negative rod will moves to the finger. After this, remove the finger and the rod. This leaves the electroscope be positively charged.