Like miniature power plants,photovoltaic cells are designed to producesteady supplies of useful, electric power. From small solar cells onelectronic calculators to completely photovoltaic roofs, their job isessentially to produce a constant supply of electricity that we canuse to power electric appliances or store in batteriesfor. Photoconductive cells such as light-dependent resistors are more likely to be used aslight detectors in such things as automated washroom. Phototubes were originally used as light detectors too, but they're relativelycumbersome, elaborate, and expensive; smaller and cheaper electroniccomponents like.