The Light-Dependent Resistor (LDR)
- A light-dependent resistor (LDR) is a non-ohmic conductor and sensory resistor
- Its resistance automatically changes depending on the light energy falling onto it (illumination)
- As the light intensity increases, the resistance of an LDR decreases
Resistance of an LDR depends on the light intensity falling on it
- This is shown by the following graph:
Graph of light intensity and resistance for an LDR
- LDRs can be used as light sensors, so, they are useful in circuits which automatically switch on lights when it gets dark, for example, street lighting and garden lights
- In the dark, its resistance is very large (millions of ohms)
- In bright light, its resistance is small (tens of ohms)
LDRs are used for automatic street lights
