What happens when two unlike materials are rubbed together and then separated?

When two unlike materials are rubbed together, a transfer of electrons occurs due to the difference in their electron affinity. This phenomenon is known as triboelectric charging. In this process, one material tends to lose electrons and becomes positively charged, while the other material gains those electrons and becomes negatively charged. This results in one of the materials having an overall positive charge and the other an overall negative charge once they are separated.

This principle is applied in various everyday scenarios, such as rubbing a balloon on hair, where the balloon becomes negatively charged as it collects electrons from the hair, which loses some electrons and becomes positively charged. The interaction and subsequent separation of these two different materials lead to their opposite charges, confirming that one will be positive and the other negative.