Which component emits light when heated?

Which component emits light when heated?

• A. Filament bulb
• B. LDR
• C. Diode
• D. Thermistor

Answer: (A)

Light emitted when something is heated comes from incandescence, where a hot object glows as it radiates visible light. A filament bulb uses a tungsten filament that is heated by electric current to a high temperature, so it glows and emits light. The other options don’t light up because they respond to light or temperature without producing light themselves: an LDR changes resistance in response to light, not to heating; a thermistor likewise changes resistance with temperature but doesn’t emit light; a diode only emits light if it’s a light‑emitting diode, which operates by a different mechanism than heating the filament. So the filament bulb is the one that emits light when heated.

Light emitted when something is heated comes from incandescence, where a hot object glows as it radiates visible light. A filament bulb uses a tungsten filament that is heated by electric current to a high temperature, so it glows and emits light. The other options don’t light up because they respond to light or temperature without producing light themselves: an LDR changes resistance in response to light, not to heating; a thermistor likewise changes resistance with temperature but doesn’t emit light; a diode only emits light if it’s a light‑emitting diode, which operates by a different mechanism than heating the filament. So the filament bulb is the one that emits light when heated.