An electroscope is an apparatus used to test the presence of electric charges. Two
aluminum strips are suspended to one end of the brass rod. The other end of the brass
rod is attached to a brass disc.
a) When the brass disc is touched with object A, the aluminum strips repel each other.
What is the nature of object A?
b) In a charged electroscope, if the brass disc is touched with hand, the aluminum strips
collapse. Why?
c) The aluminum strips of an electroscope is charged negative initially. On touching
the brass disc with a charged plastic rod, the aluminum strips diverge furthermore
away from each other. What type of charge is carried by plastic rod?
Answers
The electroscope is an early scientific instrument used to detect the presence of electric charge on a body. It detects charge by the movement of a test object due to the Coulomb electrostatic force on it. The amount of charge on an object is proportional to its voltage. The accumulation of enough charge to detect with an electroscope requires hundreds or thousands of volts, so electroscopes are used with high voltage sources such as static electricity and electrostatic machines. An electroscope can only give a rough indication of the quantity of charge; an instrument that measures electric charge quantitatively is called an electrometer.
Answer:
An electroscope is an apparatus used to test the presence of electric charges. Two
aluminum strips are suspended to one end of the brass rod. The other end of the brass
rod is attached to a brass disc.
a) When the brass disc is touched with object A, the aluminum strips repel each other.
What is the nature of object A?
b) In a charged electroscope, if the brass disc is touched with hand, the aluminum strips
collapse. Why?
c) The aluminum strips of an electroscope is charged negative initially. On touching
the brass disc with a charged plastic rod, the aluminum strips diverge furthermore
away from each other. What type of charge is carried by plastic rod?