1. Incandescent Principle: The bulb operates by passing an electric current through a thin tungsten filament inside a vacuum or inert gas-filled glass bulb. As the current flows through the filament, it encounters resistance, causing the filament to heat up.
2. High Temperature Filament: To emit visible light, the filament must reach temperatures around 2,700 to 3,300 degrees Celsius (4,900 to 6,000 degrees Fahrenheit). At such high temperatures, the filament glows brightly, producing visible light.
3. Inefficient Energy Conversion: Incandescent bulbs are not very efficient at converting electrical energy into light. Most of the energy (about 90%) is actually emitted as heat rather than visible light. This inefficiency means that a significant portion of the electrical energy input ends up heating the filament and the bulb itself.
4. Thermal Conductivity of Materials: Tungsten, the metal used in the filament, has a relatively low thermal conductivity. This means that once the filament heats up, it retains much of that heat rather than dissipating it quickly. Additionally, the glass bulb of the light bulb also retains heat to some extent, contributing to the overall warmth of the bulb.
5. Design and Safety Considerations: The bulb’s design and materials must withstand the high temperatures generated by the filament. The glass bulb is made from materials that can tolerate the heat without shattering, and the filament itself is designed to operate at high temperatures for extended periods.

Incandescent light bulbs get too hot when in use to be a sustainable lighting option. Incandescent light bulbs are history. Invest in LEDs!