John charges a plastic rod through friction by rubbing it with cotton. Touching the charged rod to the electroscope transfers the charge via conduction, resulting in the electroscope's metal leaves repelling each other, indicating a positive charge.
When John rubs a piece of cotton fabric on a plastic rod, he induces a charge on the rod through friction. He then transfers this charge to the electroscope through conduction by touching it with the charged rod. An electroscope can detect the presence of electrical charge, and it consists of a metal rod with attached gold foil leaves, all enclosed in a glass container. As only electrons can move in metals, when a positively charged rod is touched to the electroscope, electrons are attracted and transferred to the rod, leaving the electroscope with a net positive charge. As a result, the leaves, which now bear the same positive charge, repel each other and separate, indicating that a charge has been detected.
the rod becomes charged through friction with cotton and, once in contact with the electroscope, the charge is conducted, leaving the electroscope positively charged and the leaves repelled due to like charges.