🔹 What is a Resistor? A resistor is one of the most basic and widely used electronic components. It is a passive component that resists the flow of electric current, reducing voltage and controlling current in a circuit. 🔹 Symbol in Circuit: Fixed resistor: zig-zag line or rectangle (depends on standard). Variable resistor (potentiometer): arrow across the symbol. 🔹 Unit: Resistance is measured in Ohms (Ω). Large values: kilo-ohms (kΩ = 1000 Ω), mega-ohms (MΩ = 1,000,000 Ω). 🔹 Types of Resistors: Fixed Resistor – fixed resistance value. Carbon film, Metal film, Wire-wound. Variable Resistor (Potentiometer/Trimmer) – resistance can be adjusted. Special Resistors: LDR (Light Dependent Resistor): resistance changes with light. Thermistor: resistance changes with temperature. Varistor: resistance changes with voltage. 🔹 Color Code: Resistors have colored bands to indicate their resistance value. Example: Red (2), Violet (7), Brown (×10) → 270 Ω. 🔹 Applications: Limit current to protect LEDs and other components. Divide voltage (voltage divider circuits). Biasing transistors in amplifier circuits. Timing circuits (with capacitors). Pull-up and pull-down resistors in microcontrollers.