Tungsten is used as the filament material in electric bulbs because it has several properties that make it ideal for producing light through incandescence.
When an electric current passes through the filament, it gets heated due to the resistance of the material. The filament must be able to withstand very high temperatures (around 2500°C to 3000°C) without melting or evaporating quickly — and tungsten excels in this regard.
Here’s why tungsten is preferred:
- High Melting Point:
Tungsten has a melting point of about 3422°C, the highest among all metals. This allows it to glow brightly at high temperatures without melting. - High Resistivity:
Its high electrical resistance helps it heat up efficiently when current passes through, producing visible light. - Low Evaporation Rate:
Tungsten evaporates very slowly even at high temperatures, increasing the life of the bulb. - Mechanical Strength:
It is strong and can be drawn into thin wires that can handle vibration and mechanical stress. - Good Luminance:
Tungsten produces a bright white light when heated, making it perfect for illumination.
In summary, tungsten’s high melting point, strength, and efficient light emission make it the best choice for bulb filaments.