A light dependent resistor (LDR) or photoresistor or photocell is a resistor whose resistance decreases with increasing incident light intensity. Below I have shown LDR in different size (small to big).
In other words, LDR is a resistor whose resistance can be adjusted by the amount of light falling on it.
A photoresistor is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron conduct electricity, thereby lowering resistance.
APPLICATIONS
Photoresistors can be found when we need to control some device with the variation in light.
Photoresistors come in many types. Inexpensive cadmium sulphide cells can be found in many consumer items such as camera light meters, street lights, clock radios, alarm devices, outdoor clocks, solar street lamps and solar road studs, etc.
SYMBOL OF LDR
CONNECTING LDR
LDR is also a two-terminal electrical which can be connected either way, that means it have no positive and negative terminal.
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