A pith ball is suspended by a silk thread from a non-conductive stand. When a charged object (such as a hair comb) is brought close to the neutral ball, the charges inside it separate (electrostatic induction). This leads to the net attraction force between the ball and the comb (Photo 1, seen here). When the charged comb touches the ball, some charge is transferred and the ball becomes charged with the same polarity charge. As a result the comb and the ball repel each other (Photo 2). Photo 1 of 2.