Question

Describe how we use a gold leaf electroscope to detect the presence of charge on an object. Describe how we can use a gold leaf electroscope to detect the nature of charge on an object.

Answer 1

Hint: A gold leaf electroscope is a device that is used to detect the presence of charge on an object and also determine the nature of charge present. It has two gold plated strips that are called leaves that can be charged when a charged body is kept in contact with the cap that connects the two leaves.

Complete answer:
A gold leaf electroscope is a simple device that is made up of a cap that is connected with two gold plated strips called leaves that hang closely to each other. It can be used to detect the presence of charge on a body and also determine the nature of the charge on the body.
To detect the presence or absence of charge on a body, we bring the body close to the gold leaf electroscope and touch it with the cap of the device. If the body has charge, then the two leaves of the electroscope also get similarly charged. This leads to a repulsive force between the two leaves as charges repel each other and hence, the two leaves diverge. This confirms that the body has some charge on it.
To detect the nature of charge on a body, the body can be brought near an already charged electroscope. Say, the electroscope is positively charged. Now, if the body has a negative charge and is kept in contact with the cap, then the negative charge from the body will neutralize some of the positive charge in the leaves and hence, the leaves will move a bit closer (converge). If the body is positively charged, then it will increase the positive charge in the leaves of the electroscope when kept in contact with the cap and hence, the leaves will move further apart (diverge). If the body has no charge, then there will be no effect on the separation of the leaves. Therefore, in this way we can detect the nature of charge on an object.

Note:
Students must note that gold is used in the leaves of the electroscope since gold is a very ductile metal and can be made into very thin leaves of very low mass. A low mass in the leaves is extremely essential so that the small amounts of force exerted by the charges in the leaves can produce a significant deflection in the leaves which can be observed by us. If the leaves are too heavy, the deflection produced will be negligible and we will not be able to ascertain whether a body has charge or not.