A Light Dependent Resistor(LDR) or a photoresistor is a non-linear device whose resistivity is a function of the incident electromagnetic radiation.
- A light-dependent resistor works on the principle of photoconductivity.
- Photoconductivity is an optical phenomenon in which the conductivity of the material (Hence resistivity) reduces when light is absorbed by the material.
- When light falls the resistance of the device has decreased.
- When the light-dependent resistor is kept in dark, its resistance is very high. This resistance is called as dark resistance.
- It has high as 1012 ohm when LDR kept in dark.
- When the light is incident on a photocell it usually takes about 8 to 12ms for the change in resistance to take place.
- While it takes seconds for the resistance to rise back again to its initial value after removal of light.
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