A light module having a first power line, a second power line, and light devices. The first power line is connected to a first power point. The second power line is connected to a second power point. Each light device having a first terminal coupled to the first power line and a second terminal coupled to the second power line. A first sum of a first line length between the first power point and the first terminal of any of the light devices and a second line length between the second power point and the second terminal thereof is substantially a first constant.