What type of charge does a glass rod acquire when it is rubbed with silk?

Concept

When two different insulating materials are rubbed together, electrons—not protons—may transfer according to the materials' relative tendency to hold electrons.

The object that loses electrons acquires a positive net charge, while the object that gains electrons acquires a negative net charge.

Application

In the glass–silk pair, electrons move from the glass rod to the silk. The glass rod is therefore left with an electron deficit and acquires a positive charge.

Contrast

• Negative charge would require the glass rod to gain electrons; that reverses the triboelectric direction for this material pair.

• No net charge would require no charge separation, whereas rubbing unlike insulators produces such separation.

• Alternately positive and negative charge assumes the transfer direction reverses during rubbing; for a fixed material pair, the direction is consistent.

Therefore, the glass rod acquires a positive charge.