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Home Minds On Static Electricity Mission SE5 Charging by Induction - Pop Can Induction Help Help 5

Mission SE5 Charging by Induction - Pop Can Induction

The Question

Two neutral conducting pop cans are touching each other. A negatively charged balloon is brought near one of the cans. The cans are separated while the balloon is nearby. After the balloon is removed the cans are brought back together. When touching again, can Y is ____.

Physics Rules

Law of Conservation of Charge:
Charge is never created nor destroyed, only transferred between objects. When all the charge (in the form of electrons and protons) is accounted for, the total amount of charge is the same before and after any charging or discharging process. Charge is said to be conserved.

Minds On Time

In the electrostatic activities of this unit, the charging and discharging processes occur by means of the transfer of electrons between objects. In this example, the charged balloon induces a movement of electrons between the two cans. The electrons will be attracted from can Y to can X if a positively charged balloon is held nearby. And the electrons will be repelled from can X to can Y if a negatively charged balloon is held nearby. When the cans are separated, they each have an excess of opposite charge. But when they are brought back together again with the balloon no longer nearby, there is an attraction between this excess of charge. This causes another movement of electrons back to the original neutral state. This is a piece of evidence for the law of conservation of charge (see Know the Law section).

Physics Rules

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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