Question

In a filament type light bulb, most of the electric power consumed appears as:
(a) visible light (b) infra - red - rays (c) ultravioley rays (d) fluorescent light

Answer 1

An electric current heats the filament to typically 2,000 to 3,300 K (3,140 to 5,480 °F), well below tungsten's melting point of 3,695 K (6,191 °F). Filament temperatures depend on the filament type, shape, size, and amount of current drawn. The heated filament emits light that approximates a continuous spectrum. The useful part of the emitted energy is visible light but most energy is given off as heat in the near-infrared wavelengths.