1. The problem statement, all variables and given/known data 1) If one is using light bulbs to detect phase sequence then it is wise to connect them in series with circuit resistor. Why ? 2) There is short circuit in phase "A". In which case is short circuit voltage larger, in four-drive (?) system or in three-drive (?) system ? Which system is cheaper ? 3. The attempt at a solution 1) Because otherwise light bulbs would have same brightness ? Any help would be much appreciated.