What Is Ldr ?

Ldr is also known as Light Dependent Resistor 

Ldr is a type of resistor which offers high resistance when it is kept in darkness and when it is kept in-front of light it's resistance decreases .So in-short we can say that when we keep ldr in higher intensity of light it acts like a normal wire due to which high amount of current flows from it or we can say that the voltage drop across the ldr is zero.But when we keep it in darkness it offers high impedance that is we can say that the voltage drop across the ldr is high. 

Symbol of  LDR :-

Structure of LDR :-

You can see a digital wave pattern in most of the Ldr this is because it increases the area for the light (photons) to enter into the active region making it more sensitive towards the intensity of light.It has a high resistance because there are very few electrons that are free and able to move  Therefore in this state there is a high LDR resistance.As light falls on the active region, the energy of the photons is transferred to the electrons. This gives some of them sufficient energy to break the bond and to move freely so that they can  conduct electricity. This results in a lowering of the resistance of LDR.

Applications Of LDR :-

There are many applications of Ldr you can use it many different projects like brightness controller, burglar alarms,automated street light controller,fire alarms,etc.

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