Light-Controlled Lamp

Project Number: 71

OBJECTIVE: To turn a lamp on and off using light.

Description: Cover the unit, turn the slide switch (S1) on, and notice that the lamp (L1) is off after a few seconds. Place the unit near a light and the lamp turns on. Cover the photoresistor (RP) and place it in the light again. The lamp will not turn on. The resistance of the photoresistor decreases as the light increases. The low resistance acts like a wire connecting point C to the positive (+) side of the battery (B1).