# What does a LDR do in a circuit GCSE?

## What does a LDR do in a circuit GCSE?

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 the difference between an LED and LDR?

LED is an output device, this generates light when current flows through it. LDR is a light sensitive resistor, which changes resistance according to the light intensity. It is mainly used for sensing purpose. Overall LED is a semiconductor, LDR is a resistor.

What is the working principle of LDR?

The working principle of an LDR is photoconductivity, which is nothing but an optical phenomenon. When the light is absorbed by the material then the conductivity of the material enhances. When the light falls on the LDR, then the electrons in the valence band of the material are eager to the conduction band.

### How does an LDR work BBC Bitesize?

LDRs (light-dependent resistors) are used to detect light levels, for example, in automatic security lights. Their resistance decreases as the light intensity increases: in bright light, the resistance of an LDR is low and more current can flow through it.

How do you calculate current in an LDR?

It’s page 71 of the Nelson Thornes AQA AS Physics book. A light sensor consists of a 5.0V cell, an LDR and a 5.0k Ohm resistor in series with each other. A voltmeter is connected in parallel with the resistor. When the LDR is in darkness, the voltmeter reads 2.2V.

As its name implies, the Light Dependent Resistor (LDR) is made from a piece of exposed semiconductor material such as cadmium sulphide that changes its electrical resistance from several thousand Ohms in the dark to only a few hundred Ohms when light falls upon it by creating hole-electron pairs in the material.

What are the different types of LDR?

According to the spectral characteristics of LDRs, there are three types of LDRs: – Ultraviolet LDR: more active to ultraviolet light, including cadmium sulfide, cadmium selenide LDR, etc., used for UV exploration. – Infrared LDR: Lead sulfide, lead telluride and lead selenide are the main ones.

What are the types of LDR?