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05 – Light Dependent Resistor

The picture shows a sketch of a Light Dependent Resistor on the left and the symbol on the right. 

A light dependent resistor (LDR) is an electronic component whose resistance decreases with increasing incident light intensity. In other words when it is dark it has a high electrical resistance and when it is light it has a low electrical resistance.

The light dependent resistor is normally used in a potential divider setup with a second regular resistor to provide a voltage input for other analogue or digital circuits (more about potential dividers later). Light Dependent Resistors are used in applications where an indication of light or darkness is required such as street lights, clock radios and outdoor clocks.