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A great example of how a charge can build up in powder factories etc. Pour the talc or lycopodium powder down a plastic channel onto the top of the electroscope (a petri-dish to catch the powder keeps thing neater). The friction of the powder with the plastic channel will cause the powder to become charged, and hence the electroscope will show a charge.
The second unusual demo from the archives is to use a source of ionising radiation to charge the plate. A reasonably active source will cause the leaf to move promptly.
