Electrostatics and aluminium foil problem

[yipkawa]

1' after a metal rod rubbing with a cloth, is the metal rod remains neutral in charge whereas the cloth will be positive charge?
2' a small pieces of paper and aluminium foil are attracted by charged metal rods when the rods are brought close to them. however, the former stick to the rod while the latter not. why?

 

[OlderDan]

1' after a metal rod rubbing with a cloth, is the metal rod remains neutral in charge whereas the cloth will be positive charge?
2' a small pieces of paper and aluminium foil are attracted by charged metal rods when the rods are brought close to them. however, the former stick to the rod while the latter not. why?

What do you think happens in #1? How are a piece of paper and aluminum foil different in terms of their electrical properties?

 

[yipkawa]

What do you think happens in #1? How are a piece of paper and aluminum foil different in terms of their electrical properties?

is it one of them is conductor but the other one not?

 

[OlderDan]

is it one of them is conductor but the other one not?

That is the important difference between the paper and the aluminum. When the paper is attracted and sticking to a charged rod it is because of a slight realignment of the charges in the paper. This is called polarization. The paper usually remains neutral, so the attraction continues.

When a piece of aluminum touches a charged rod, charge is transferred from the rod to the aluminum. Both objects wind up with the same excess charge and so they repel one another.