The electrical charge that builds up by friction between two dissimilar materials is called static electricity.

Here's a breakdown:

* Friction: The rubbing action between the two surfaces causes electrons (negatively charged particles) to be transferred from one material to the other.

* Dissimilar materials: Materials have different abilities to hold onto their electrons. This difference in "electron affinity" is key to static electricity.

* Charge separation: The material that gains electrons becomes negatively charged, while the material that loses electrons becomes positively charged.

Examples:

* Rubbing a balloon on your hair: Electrons transfer from your hair to the balloon, making the balloon negatively charged and your hair positively charged.

* Walking across a carpet in socks: Electrons transfer from the carpet to your socks, making you negatively charged. This can lead to a shock when you touch a metal object, like a doorknob.

Let me know if you'd like to know more about static electricity!