Question

The device used to detect the presence of static electric charges on a body is called:
(A) Ammeter
(B) Gold leaf electroscope
(C) Voltmeter
(D) Microscope

Answer 1

Hint: Static electric charge is better known as static electricity. Static electric charge or static electricity is an imbalance of electric charges within or on the surface of a material. Unlike electric current which constitutes moving charges, static electricity remains stationary at a place unless moved by external agents.

Complete step by step answer:
An electroscope is a device that detects static electricity by using thin metal or plastic leaves, which separate when charged. An electroscope works on the principle that static charges can be transferred using physical contact and like charges repel each other.
A gold-leaf electroscope is one of the most sensitive electroscopes. A metal disc is connected to a narrow metal plate and a thin leaf of gold is fixed to the gold. The entire setup of the gold leaf is insulated from the body of the instrument. When a charge is put on the disc at the top of the electroscope, it spreads down to the plate and the leaf. Now the leaf and the plate both have the same charge and since like charges repel each other, the leaf moves away from the plate. The bigger the magnitude of the static electric charge, the higher the leaf rises away from the plate.
After the above discussion, we can say that the gold leaf electroscope is used to detect the presence of charge on a body and hence option (B) is the correct answer.

Note: Let’s say we don’t know about electroscopes or gold leaf electroscopes, how will we proceed then?
We can analyse the other options given to us. An ammeter is used to measure the magnitude of electric current flowing in a circuit. A voltmeter is used to measure the potential difference across any two points. A microscope is used for magnification and study of minute organisms. Hence we can see that none of these options relates to static charges. The only option left now must be our answer.