Why bright dim capacitor for measuring phase sequence?

A bright dim capacitor is used for measuring phase sequence because it allows for a visual indication of the phase relationship between the voltages in a three-phase system. When connected to the phases, the capacitor causes a change in brightness of the lamp based on the phase sequence, with the brightness varying depending on whether the phases are in the correct order or not. This method provides a simple and effective way to identify phase rotation without needing complex instruments.