A comb on rubbing with our hair gets charged by a method known as the frictional charging method. Either our hair or comb one of them is more electropositive, let say comb. On rubbing, heat is produced, which increases the kinetic energy of valence electrons in atoms of comb, which results in the ionization of these electrons. So comb will lose electrons while hairs will gain
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So an equal amount of positive and negative charge will arise on comb and hairs, respectively.
In the same way, a balloon gets charged on rubbing with hairs. This charged ballon gets attached to the wall. This balloon attaches to the wall by a method known as induction.
As atoms of the wall are neutral, having no charge, this charged balloon will attract the electrons repel the electrons from the atom of the wall depending on which type of charge is on it.
If positively charged, it will attract the electrons, and if it is a negative charge, it will repel the electrons from the atoms of the wall. In both cases, what happens is that the opposite charge is near to each other that is, the charge on the balloon is opposite to the charge on the wall near the balloon. The portion of the wall farther from the balloon has the same charge as that on the balloon.
Like charges attract each other and unlike charges, repel each other, so the portion nearer to the balloon will attract it while the portion of the wall is far from the balloon but will repellballon.
The distance between the portion nearer to the ballon will be smaller, so the attractive force will be larger than the repulsive force, and thus balloon will be attracted toward the wall.
In the same way, small paper pieces are also attracted toward the charged rod or charged comb. When a charged comb or charged rod is taken to the small paper pieces, then induction also takes place in paper them that is the redistribution of the electrons. The nearer ends get opposite polarity while farther ends get a similar polarity. If the rod is positively charged, the end of the paper piece near the rod will negatively charge. If the rod is negatively charged, then the end of a paper piece nearer to the rod will get a positive charge, while the end of the paper farther from the rod will get an opposite charge. As like charges attract and we know that less is the distance between the charges more is force. As nearer ends have unlike charges, the force of attraction between unlike charged ends nearer to each other will be more than the repulsive force between the farther ends of a paper piece and rod, respectively.
There will be a net force of attraction between paper pieces and charged rod or charged comb. So paper pieces and charged rod a charged on will attract each other with some force.
So here we come to know how a comb or rod gets charged on rubbing with silk or with hair and how these charged insulators attract small paper pieces and dust particles.
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