Question

Why do a rubbed comb attrack paper pieces?

Answer 1

When we run a comb, static charges are created in the comb.
When bring them near to paper pieces,like charges repel and unlike charges accumulate in the near ends of paper and comb.
Thus they attract as unlike charges attract each other.

Answer 2

when comb is rubbed it gets charged due to electron transfer between them...
this charge transfer takes place by the process of rubbing...

And when rubbed electron transfer takes place making the neutral comb to charged one..

Now this charged comb when come closer to small piece of paper it repels the like charge and opposite charges are created and hence paper gets attracted.....