When current passes through the filament of an incandescent lamp, electric power is released on it:
P = U * I = U² / R.
P – power;
U is the voltage;
R is the resistance of the spiral.
It can be seen that if you reduce the voltage, and the resistance of the lamp remains constant, then the power allocated to the lamp will also decrease.
The glow of an incandescent lamp occurs due to the fact that part of the power when the lamp is heated (incandescent) is emitted in the form of radiation in the light range.
The power decreases – the lamp heats up less, less light radiation.
An insufficiently hot spiral has a reddish tint.
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