Can you tell me which one of the following statements best explains why tiny bits of paper
are attracted to a charged rubber rod?
Now the rubber rod is an insulator, and the paper is also an insulator, since they use it in
capacitors it would seem that to attract paper the rubber rod would have to repel electrons in
the paper which would leave a surface charge of + then they would attract
Possible answers:
1. Paper is positive material,
2. Paper is negative material,
3. Paper becomes polarised by induction
4. Rubber and paper attract each other
5. Paper acquires a net positive charge by induction
The charges in the paper are polarised. Those of
similar charge to the excess charge on the rod are repelled and those of opposite charge are
attracted. This leaves an area of opposite charge near the rod and so since the paper scraps
are so light they can be lifted up by this attraction.
So – the last answer is not
correct. The charge on the paper remains the same – it is just that this charge is distributed
differently.
The correct answer is number 3: Paper becomes polarised by
induction.