Which device is used to detect light levels in automatic lighting systems in many circuits?

Which device is used to detect light levels in automatic lighting systems in many circuits?

• A. Thermistor
• B. Light-dependent resistor
• C. Capacitor
• D. Inductor

Answer: (B)

A light-dependent resistor is used to sense ambient light in automatic lighting systems. Its resistance changes with how much light shines on it—high in darkness and lower as light increases. In a typical circuit, it sits in a voltage divider so the output voltage varies with light level. That varying signal is then sent to a switch or controller to turn lights on when it gets dark and off when it’s bright enough. This makes it ideal for dusk-to-dawn or street-light sensors. The other components don’t detect light: a thermistor responds to temperature, a capacitor stores charge, and an inductor responds to changing currents and magnetic fields.

A light-dependent resistor is used to sense ambient light in automatic lighting systems. Its resistance changes with how much light shines on it—high in darkness and lower as light increases. In a typical circuit, it sits in a voltage divider so the output voltage varies with light level. That varying signal is then sent to a switch or controller to turn lights on when it gets dark and off when it’s bright enough. This makes it ideal for dusk-to-dawn or street-light sensors. The other components don’t detect light: a thermistor responds to temperature, a capacitor stores charge, and an inductor responds to changing currents and magnetic fields.