Incandescents

Incandescents are electric light sources that emit light primarily by heating a metal filament to incandescence. The most common design uses a tungsten filament enclosed in a glass bulb filled with an inert gas or a vacuum. When electric current passes through the filament, resistance converts energy into heat, raising the filament’s temperature until it radiates visible light over a broad spectrum.

Construction and variants: Standard incandescent bulbs consist of a tungsten filament mounted inside a glass envelope. Tungsten halogen bulbs add a halogen gas, allowing tungsten to cycle back to the filament and extending life while maintaining a bright, high-temperature operation. Other variants include reflector shapes and decorative forms, all sharing the basic principle of light produced by a hot filament.

Efficiency and lifespan: Incandescents have relatively low luminous efficacy compared with modern lighting, typically around 10–17 lumens per watt for standard bulbs. Lifespans are commonly about 750–2,000 hours, shorter for higher wattage. Tungsten halogen bulbs offer modest improvements in efficiency and longevity but remain far less efficient than LEDs or compact fluorescent lamps. They also generate substantial heat.

Regulation and use: Many jurisdictions have phased out or restricted traditional incandescent lamps in favor of more efficient technologies, with exemptions for specialty or decorative applications. Despite regulatory changes, incandescents remain valued for their simplicity, instant full brightness, and excellent color rendering, particularly in settings where dimming and warm light are desirable. They are still used in some decorative, appliance, and photography contexts where their light characteristics and heat output are advantageous.