Which type of circuit component generally causes a humming sound in incandescent lamps when using dimmers?

The humming sound in incandescent lamps when using dimmers is primarily caused by the operation of triacs. Triacs are semiconductor devices that control the power delivered to the lighting load by rapidly switching on and off as part of the dimming process. When the triac turns on and off at a high frequency, it can cause mechanical vibrations in the components of the lamp, leading to the perceptible humming sound.

This effect is more pronounced at lower dimming levels, where the triac adjusts the power to the light bulb. The switching action does not match the steady flow of current in standard operation, resulting in these vibrations that manifest as a noise. Understanding this behavior helps in selecting appropriate dimming technologies and predicting their performance in residential wiring applications.