Question

When you rub a glass rod with a piece of silk, the glass rod becomes positively charged?

Answer 1

Explanation :

When a glass rod is rubbed with a piece of silk the glass rod becomes positively charged. The charge appears due to the friction. On rubbing the electrons from glass gets transferred to silk cloth.  

We know that the element that loses electron is positively charged and the element which gains an electron is negatively charged.  Thats why the glass rod is positively charged.

Hence, this is the required explanation.

Answer 2

Glass loses electrons easily and silk takes them. Because electrons are negatively charged, the glass rod becomes positive and the silk becomes negative.