Hi Pritam, I think there is a little correction in your question

Actually you can't charge any conductor by rubbing it, only insulators can be charged by rubbing.

When a conductor is rubbed, any excess charge acquired is quickly redistributed and spread evenly throughout the conductor. This redistribution occurs due to the high mobility of free electrons within the conductor. As a result, the charge is rapidly neutralized or dissipated, and the conductor does not retain the charge for an extended period.