Charging materials by friction
2 marks · EasyExplain why metal objects cannot be charged by friction in the same way as plastic rods.
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Metals are conductors, so electrons move through them and the charge cannot stay on the surface.
Also accept: Metal allows electrons to flow away, so charge does not build up.; Electrons cannot remain on a metal surface because it is a conductor.
Common mistakes: Suggesting metals cannot gain/lose electrons at all
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Marking points
B1 · 1 mark · Identifies that metals are conductors.
B2 · 1 mark · Explains that charge cannot stay on the surface (leaks away).
Worked solution
Metals are conductors. Any extra electrons move easily through the metal and away, so the object does not retain the charge.