It is important to know the atomic picture of matter. The basic unit of all matter is an 'atom'. Each atom consists of a small core called nucleus which accounts to most of its mass consisting of positively charged protons and neutral neutrons and surrounded by lighter negatively charged particles called electrons.
The negative charge of the electron has exactly the same magnitude as the positive charge of the proton. If one or more electrons are removed from the neutral atoms, the remaining positively charged particlesare called positive ions. A negative ion is an atom that has gained one or more electrons.
It is clear that usually the negative charge is transferred when two bodies are rubbed together. The electrons that are less tightly bound tend to move from its atom to the other. The number of electrons that are transferred will be insignificant compared to the total number of electrons or protons in the body. Thus the charge acquired by friction is a very small fraction of the total positive and negative charge content in a body .
Connect a charged plastic rod to an uncharged pith ball through a copper wire. Instantly the ball gets charged.
