日光灯使用一段时间后,灯管两头会发黑,这时可将灯管旋转180。(如图C)再使用就能提高发光效率,还能延长使用寿命。道理如下:日光灯管在点燃时,灯管二端灯丝温度A、B二点高于C、D二点。当A、B二点附近发黑时,C、D二点往往还未老化。所以,日光灯使用一段时间后,如图(C)将灯管 Fluorescent use of a period of time, the lamp will be black at both ends, then the lamp can be rotated 180. (Figure C) reuse can improve luminous efficiency, but also extend the service life. The reason is as follows: Fluorescent tube is lit, the two ends of the filament filament temperature A, B two points higher than C, D two. When A, B black near the two, C, D two points are often not aging. Therefore, the use of fluorescent lamp after a period of time, as shown in Figure (C) lamp