How does a light Dependant resistor work?
How does a light Dependant resistor work?
Working Principle of LDR. These devices depend on the light, when light falls on the LDR then the resistance decreases, and increases in the dark. When a LDR is kept in the dark place, its resistance is high and, when the LDR is kept in the light its resistance will decrease.
What is a light dependent resistor called?
Photoresistors, also known as light dependent resistors (LDR), are light sensitive devices most often used to indicate the presence or absence of light, or to measure the light intensity.
What is a light dependent resistor GCSE?
The LDR. LDRs (light-dependent resistors) are used to detect light levels, eg in automatic security lights. Their resistance decreases as the light intensity increases. In the dark and at low light levels, the resistance of an LDR is high, and little current can flow through it.
What is LDR PPT?
LDR(LIGHT DEPENDENT RESISTOR) • A light dependent resistor (LDR) or a photo resistor or photocell is a light controlled variable resistor . Its resistance changes with Light intensity that falls on it. • The resistance of a photo resistor decreases with increasing Incident light intensity .
What are the two types of light dependent resistor?
Light dependent resistors, LDRs or photoresistors fall into one of two types or categories: Intrinsic photoresistors: Intrinsic photoresistors use un-doped semiconductor materials including silicon or germanium. Photons fall on the LDR excite electrons moving them from the valence band to the conduction band.
What is the function of Photoresistor?
Photoresistors are used in streetlights to control when the light should turn on and when the light should turn off. When the surrounding light falls on the photo resistor, it causes the streetlight to turnoff. When there is no light, the photoresistor causes the street light to turn on.
What is the resistance of light dependent resistor?
Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are illuminated with light resistance drops dramatically. The animation opposite shows that when the torch is turned on, the resistance of the LDR falls, allowing current to pass through it.
What is the symbol of LDR?
resistor circuit symbol
The LDR symbol used in electronic circuits is based around the resistor circuit symbol, but shows the light, in the form of arrows shining on it. In this way it follows the same convention used for photodiode and phototransistor circuit symbols where arrows are used to show the light falling on these components.
Who invented light dependent resistor?
The idea of Photoresistor developed when photoconductivity in Selenium was discovered by Willoughby Smith in 1873. Many variants of the photoconductive devices were then made.
What is the function of a light dependent resistor?
A light dependent resistor, or LDR, varies resistance in a circuit based on how much light shines on it. When fully illuminated, the LDR has no resistance and current flows freely, but with darkness the resistance increases and current flow stops.
What does light dependent resistor mean?
LDR or Light Dependent Resistor (popular as photoresistor) is an electrical device whose resistivity is a dependent on the light falling on it . In other words they are light-sensitive resistors , Also known as photo-conductive, photo-conductors cells (or photocells), they are made up of semiconductor materials with high resistance values.
How do light dependant resistor(LDR) works?
An LDR is a type of variable resistor which changes its resistance according to the intensity of the light falling on its surface.
What is a voltage dependent resistor?
A varistor is a voltage dependent resistor (VDR). The resistance of a varistor is variable and depends on the voltage applied. The word is composed of parts of the words “variable resistor”. Their resistance decreases when the voltage increases. In case of excessive voltage increases, their resistance drops dramatically.
