Charging materials by friction
2 marks · EasyExplain what happens, in terms of electrons, when a glass rod is rubbed with a silk cloth.
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Electrons move from the glass rod to the silk cloth. The glass rod loses electrons and becomes positively charged; the silk gains electrons and becomes negatively charged.
Also accept: The glass rod loses electrons to the silk.; Glass is left with fewer electrons (positive), silk with more (negative).
Common mistakes: Saying protons move
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Marking points
B1 · 1 mark · Correctly states electrons move from glass rod to silk cloth.
B2 · 1 mark · Explains glass rod becomes positively charged, silk becomes negatively charged.
Worked solution
Electrons move from the glass rod to the silk cloth, so the glass rod becomes positive and the silk becomes negative.