A photocell is an electronic device that changes its electrical resistance when light shines on it. In darkness, it has a high resistance; in bright light, the resistance drops. Electronic circuits use photocells as light-based triggers. A change in the device̵7;s resistance turns the circuit on, which performs an action. For example, a store̵7;s entrance has a photocell circuit with a steady light shining on it. A person entering the store interrupts the light, putting the photocell in darkness. The circuit rings a bell, signalling to the clerk that he has a customer. You can disable the photocell by shining another light at it.
Instructions
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1
Examine the photocell, the light that shines on it and the path the light takes toward the photocell.
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2
Turn the flashlight on and shine it at the photocell.
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3
Move the flashlight to within a few inches of the photocell. Set the flashlight so it shines steadily at the photocell and does not move. As long as the flashlight shines on the photocell, the photocell cannot trigger the circuit to which it is connected.
