gōng / chéng / shī / tōng / guò / tiáo / jié / biàn / zǔ / qì / lái / kòng / zhì / dēng / pào / de / liàng / dù工程师通过调节变阻器来控制灯泡的亮度。The engineer controls the bulb's brightness by adjusting the variable resistor.