How your calculator works is surprisingly controversial

Solar calculator casio fx115ES cropThe calculator to the left is solar powered, via the little solar panel at the top right. Small cheap solar panels like those in calculators are made from amorphous silicon, because its a lot cheaper than its more efficient but pricey, cousin crystalline silicon. In crystalline silicon the silicon atoms are arranged in a regular crystal lattice — as it happens the arrangement is similar to that of water molecules in ice.

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