When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge.

When a glass rod is rubbed with a silk cloth, electrons are transferred from the glass rod to the silk cloth.

• The glass rod loses electrons, becoming positively charged.
• The silk cloth gains an equal number of electrons, becoming negatively charged with a magnitude equal to the positive charge on the glass rod. Before rubbing, both the glass rod and the silk cloth are electrically neutral, so the total charge of the system is zero. After rubbing, the positive charge on the glass rod and the negative charge on the silk cloth sum to zero. Thus, the net charge of the isolated system remains constant (zero), which is consistent with the law of conservation of charge.