When objects become charged through friction, it's a result of the movement and transfer of electrons between the surfaces of those objects. This process is often referred to as the triboelectric effect. Here's a simplified explanation of how it works:
Electron Transfer: Atoms are composed of positively charged protons in the nucleus and negatively charged electrons orbiting around the nucleus. When two different materials are rubbed or brought into contact and then separated, the friction can cause electrons to move from one material to the other. The material that loses electrons becomes positively charged (due to an excess of protons) and the material that gains electrons becomes negatively charged (due to an excess of electrons).
Difference in Electron Affinities: The key factor in the triboelectric effect is the difference in electron affinities between the two materials involved. Electron affinity is a measure of how strongly an atom or material attracts electrons. Materials with a higher electron affinity tend to pull electrons from materials with lower electron affinity when they come into contact.
Contact and Separation: When two materials with different electron affinities are rubbed or pressed together, the electrons tend to migrate from the material with lower electron affinity to the material with higher electron affinity. As a result, one material ends up with an excess of electrons (negatively charged) and the other material ends up with a deficit of electrons (positively charged).
It's important to note that not all materials will exhibit the triboelectric effect to the same degree. Some materials have very strong electron affinities and tend to readily gain or lose electrons, while others might have weak electron affinities and show minimal charging effects.
The triboelectric effect is responsible for various everyday phenomena, such as rubbing a balloon against your hair to make it stick to the balloon or shuffling your feet on a carpet and then experiencing a static shock when you touch a doorknob. This effect has been harnessed for practical applications like generating static electricity for certain scientific instruments and devices.
Remember that this is a simplified explanation, and the exact mechanisms can be more complex due to factors like the nature of the materials, surface roughness, temperature, and humidity.