Which component changes resistance with light levels?

Which component changes resistance with light levels?

• A. Lamp
• B. Ohmmeter
• C. Light dependent resistor
• D. LED

Answer: (C)

The light dependent resistor changes resistance with light levels. It’s a photoresistor made from a semiconductor, so more light creates more charge carriers and lowers its resistance, while darkness leaves very few carriers and makes the resistance very high. This behavior lets it act as a light sensor in circuits—for example, in a voltage divider feeding a microcontroller to sense ambient light. Other items listed don’t vary their resistance with light in the same purposeful sensing way: a lamp is a light source, an ohmmeter measures resistance, and an LED’s behavior is based on forward current for emitting light, not on ambient light changing its resistance.

The light dependent resistor changes resistance with light levels. It’s a photoresistor made from a semiconductor, so more light creates more charge carriers and lowers its resistance, while darkness leaves very few carriers and makes the resistance very high. This behavior lets it act as a light sensor in circuits—for example, in a voltage divider feeding a microcontroller to sense ambient light. Other items listed don’t vary their resistance with light in the same purposeful sensing way: a lamp is a light source, an ohmmeter measures resistance, and an LED’s behavior is based on forward current for emitting light, not on ambient light changing its resistance.