Part 4/10:
In a typical photocell setup, three primary components work synergistically: the photoresistor, an ordinary resistor, and a thyristor. The thyristor acts like a power switch, preventing the lamp from activating unless it has the requisite control input. When the photoresistor operates under low light conditions, it permits enough current to flow to the thyristor's gate, allowing the light to turn on. Conversely, with increasing light, the photoresistor diverts current that would otherwise keep the thyristor activated, thereby switching the light off.