You already know that electrons have a negative charge, and the nucleus of the atom is positive. Scientists have long been shown that negatively charged particles are attracted to the particles, which are charged positively. Conversely, if the particles are charged the same way (positively or negatively), then they will repel each other.
Subjects while in the normal state, are not drawn to each other because they have a number of positive and negative charges are the same. About such subjects say that they do not have electrical properties. However, when the friction electrons are transferred from one object to another. This is the subject, where he became more electrons, it becomes negatively charged and the other positively. And they get attracted.
Want to see how it happens? Take a regular plastic comb and a good Rushashi hair comb. And now again held the comb to the hair. They will get attracted to the comb!
This happened because, while you were combing her hair, some of the electrons from the hair moved on to the comb. Electrons, as you remember, have a negative charge. So, comb, too, has acquired a negative charge - electrify because. And hair loss of some electrons, has acquired a positive charge. And now the hair and comb have charges opposite direction - negative and positive - they are attracted to each other.