Electric Forces

Science — First Preparatory

Ways of charging objects

Comparison aspect	Main idea	Keywords
1. Charging by rubbing	when two different objects are rubbed together electrons move from one to the other. A glass rod rubbed with silk loses electrons and becomes positive. A plastic ruler rubbed with wool gains electrons and becomes negative. Only electrons move protons stay inside the nucleus	differentobjectsrubbedtogether
2. Charging by conduction	when a charged object touches a neutral conductor part of its charge passes to the conductor. The neutral object then gains a charge of the same sign	chargedobjecttouchesneutral
3. Charging by induction	we bring a charged rod near a neutral metal sphere without touching it. The electrons in the sphere move away from or towards the rod so the side near the rod gets the opposite charge and the sphere is attracted to the rod. If we connect the sphere to the earth while the rod is still near it electrons flow into or out of the sphere so it ends up with a charge opposite to that of the rod	bringchargednearneutral

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