Question

Why glass rod is rubbed by silk cloth produce positive charge?

Answer 1

The core has positive charge, the electrons have negative charge. When you are rubbing the glass rod with the silk cloth, electrons are stripped away from the atoms in the glass and transferred to the silk cloth. This leaves the glass rod with more positive than negative charge, so you get a net positive charge.

Answer 2

because the negative charge from the glass rod transfers to the silk cloth