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Charging by friction, contact, induction
Beginner
Three ways to charge objects.
Friction transfers electrons between materials; contact shares charge with a touching body; induction charges a conductor without contact by bringing a charged object near and earthing.
Gold-leaf electroscope charged by induction.
Induction produces opposite charge on the nearest side.
In more detail
Objects can be charged by friction, where electrons transfer between materials, by contact, where charge flows between touching objects, or by induction, where a nearby charge rearranges charges without touching.
Real-world uses
- Rubbing a balloon on hair charges it by friction.
- Electrostatic paint sprayers charge droplets by induction.
- Dust clings to a balloon rubbed on hair, showing charging by friction, while a charged ruler can attract paper bits by induction.
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Frequently asked questions
Can induction leave an object charged?
Yes, if the induced charge is removed while the inducing charge is still nearby, the object keeps a net charge.
Why does friction charge things?
Materials hold electrons with different strengths, so electrons move from one to the other when rubbed.
What is charging by induction?
Bringing a charged object near a neutral conductor causes charge to move, and then the conductor is earthed to leave it charged.
Related topics in Electrostatics
Electric charge · Conductors and insulators · Conservation of charge · Quantisation of charge · Coulomb's law