Science · 6 pages · 12 min

Why an incandescent bulb wastes most of its energy as heat

A hot filament radiates mostly infrared, so only a slice of its output is light you can see.

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From the opening

An incandescent bulb wastes most of its energy as heat because the filament is a hot body, and a hot body radiates a broad spectrum that peaks outside the visible. You see the share that lands in visible wavelengths, and you feel the larger share as warmth. The opening covers why a hot wire radiates infrared, what the glass is actually for, and why still hotter shifts the spectrum.

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Inside

Why a hot wire radiates infrared
What the glass is actually for
Why still hotter shifts the spectrum
How dimming makes the share worse
Where the idea stops applying
A distinction worth keeping

Sources

Thermal radiation from a hot tungsten filament
A spectrum that peaks in the infrared rather than the visible

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Why an incandescent bulb wastes most of its energy as heat

From the opening

Inside

Sources

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