Question

A charged rod attracts bits of dry cork which after touching the rod often jump violently away from it .why​

Answer 1

The charged rod due to its charge attracts bits of dry cork , as the dry cork being oppositely charged gets attracted to the rod.

But in contrast to this,

When dry cork touches the rod, it borrows the charge from the rod and gets the same charge as the rod and being similarly charged, they repel....

As

Like Charges repel and Unlike charges attract each other!!

Hope it helps!!

Thanks!!

Answer 2

it's electrostatic force of attraction the basic principle behind this experiment.