Question

What is the use of LDR?

Answer 1

An **LDR (Light Dependent Resistor)** is a type of resistor whose resistance changes based on the amount of light falling on it. It is also known as a **photocell** or **photoresistor**.

### How it works:
- When there is **more light**, the resistance of the LDR **decreases**.
- When there is **less light** or darkness, the resistance of the LDR **increases**.

### Uses of LDR:
1. **Light Sensing:**
   - LDRs are commonly used in circuits where the amount of light needs to be detected. For example, they are used in **street lights** that automatically turn on when it gets dark and turn off when it's bright.

2. **Brightness Control:**
   - LDRs are used in **brightness control circuits** like in **television** or **monitor displays**. They adjust the brightness of the screen based on the surrounding light.

3. **Automatic Night Lamps:**
   - LDRs can control **night lamps** to turn them on automatically when the surrounding light falls below a certain level.

4. **Security Systems:**
   - They are used in **burglar alarm systems**. For example, an LDR can detect the opening of a window by noticing a change in light levels when the light enters through the window.

5. **Solar Tracking Systems:**
   - In solar panels, LDRs can help **track the sun's position** to keep the panels facing the sun for maximum energy generation.

### In summary:
LDRs are used in many applications where the presence or absence of light needs to be monitored or controlled, making them essential for automatic light-sensing tasks.