What were the key parts of the carbon-filament lamps developed by Joseph Swan and Thomas Edison?

The carbon-filament lamps developed by Sir Joseph Wilson Swan and Thomas A. Edison were defined by several essential components that allowed for practical electric lighting:12

• Carbon Filament: This was the light-emitting element. Swan utilized materials such as carbonized paper and cotton thread treated with sulfuric acid, while Edison experimented with carbonized thread, bristol board, and eventually bamboo.1
• Evacuated Glass Bulb: The filament was housed within a glass bulb from which air had been removed using a vacuum pump (such as those developed by Hermann Sprengel and Sir William Crookes). This vacuum was critical, as it prevented the carbon filament from oxidizing and burning away rapidly when heated.12
• Sealed Cap and Electrical Connections: The two ends of the carbon filament were brought out through a sealed cap at the base of the bulb, providing the necessary connection to an external electric supply.1

By heating the filament to incandescence via an electric current, these lamps produced steady light, marking a significant advancement over earlier, cumbersome arc lamps.12