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Charging by Induction:
Charging by induction is a charging process that involves charging an object without touching the object to a charged object. The charged object is brought near to the object to be charged (a neutral object). The charged object's presence induces a movement of electrons within the neutral object, causing it to become polarized. Then the neutral object is touched to a ground, causing a transfer of electrons between ground the neutral object. The ground is pulled away, the charged object is pulled away and the neutral object has been charged. When the process is complete, both objects are charged with the opposite type of charge.
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Many students have the misconception that induction charging involves the transfer of electrons between the charged object and the object being charged. But don't be fooled! There is no such electron movement. In this question, the charged balloon is brought near to the pop can but does not touch it. The can and the balloon are separated by a few centimeters of air. Air is an insulator. Electrons need a conducting pathway in order to move from one location to another. The insulating qualities of air prevent this movement of electrons.
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The role of the balloon in this induction charging process is to polarize the two can system by inducing a movement of electrons from one can to the other can. A negatively charged balloon repels electrons and causes many of them to move from can X to can Y. A positively charged balloon attracts electrons and causes many of them to move from can Y to can X. This movement of electrons leaves one can with a negative charge and the other with a positive charge. The two-can system is then said to be polarized.
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