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Two neutral conducting pop cans are touching each other. A negatively charged balloon is brought near one of the cans. As the balloon approaches, some _____.
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Opposites attract. Likes repel. And only electrons can move. That's the key to understanding charging by induction. When the balloon is brought near can X, a movement of electrons is induced within can X and can Y. Which way do electrons move? The answer centers around the slogan opposites attract and likes repel. Electrons are negatively charged and thus are repelled by the presence of a nearby negatively charged balloon. And being negatively charged, electrons are attracted by the presence of a nearby positively charged balloon. One thing is certain in all this discussion - protons never move! See Don't Be Fooled!! section.
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Many students have the misconception that the presence of a negatively charged object will attract protons in a neutral object and move the protons closer. But don't be fooled! Protons are indeed positively charged and attracted to negatively charged objects, but they are present in the nucleus of atoms and as such are tightly bound in that location. The charging of objects always occurs by a movement of electrons - either off an object or onto an object. Protons never move.
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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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