How does static electricity form?

Static electricity forms primarily through friction between unlike substances. When two different materials come into contact and are then separated, electrons may be transferred from one material to the other. This transfer results in one material becoming positively charged and the other becoming negatively charged. The phenomenon is commonly observed when rubbing certain materials together, such as a balloon against hair or socks on a carpet, leading to the accumulation of static charge.

The other options do not accurately describe the primary mechanism behind the formation of static electricity. Chemical reactions can generate charged particles, but they typically do not lead to the static electricity we observe in everyday life. Excessive heat exchange can influence electrical systems and cause failures, but it is not a direct means of generating static electricity itself. Electrical discharges refer to the release of static electricity, such as lightning or a spark, rather than the process of its formation. Hence, friction between unlike substances is the key factor in generating static electricity, making it the correct answer.