Question

when we rub two objects together they become electrically charged . where did this electric charge cone from?

Answer 1

This electric charge comes from the exchange of electrons between them..

Answer 2

It should be noted that even when the same material is rubbed on itself, there will be a charge displacement (plastic wrap for instance), hinting at more complexity than the triboelectric series. I seem to remember reading that some polar materials can become induced electrets under these circumstances