Question

A Van Der Graaf generator is used to build up charges on the outside of a sphere. A belt is charged with electrons by rubbing against a rough pulley. These electrons are then transferred to a metal sphere and spread out even on its outer surface. When neutral objects are brought near the sphere, they are attracted to the sphere before they touch each other.

A student claims that if an object brought near the sphere is attracted to it, then the object must be positively charged. What is the best assessment of this statement?


A) It is correct because opposite charges attract.
B) It is incorrect, the object must be negatively charged.
C) It is incorrect, the object will gain negative charges by conduction.
D) It is incorrect because neutral objects will be polarized by induction.

Answer 1

D) It is incorrect because neutral objects will be polarized by induction.

Step-by-step explanation:

Neutral objects will have an induced positive charge. This will create an attraction between a neutral object and the negatively charged sphere. So, the correct choice is that it is incorrect because neutral objects will be polarized by induction.

Answer 2

Answer: D) It is incorrect because neutral objects will be polarized by induction.

Explanation:

Charging by conduction takes place when a charged object is brought in contact with an uncharged object. The charge transfers till both the objects have equal charge.

For charging by induction, an uncharged object is brought near a charged one. opposite charge is induced at the surface near the charged one and hence, the two objects attract each other. Basically, in charging by induction, the neutral object gets polarized.

Thus, the claim of the student is incorrect. The neutral object is brought close to the charged sphere and it gets polarized by induction. The side near the charged sphere gets oppositely charged and hence is attracted towards the surface.