A.They want to spend more time with their children. B.Visiting can help the children learn history better. C.They themselves like traveling very much. D.They want to meet their children's requirements.
【简答题】某白炽灯接在220V的电源上能正常发光。如果电压减少为110V,则( )。A. 电流不变 B.电流成为原来的2倍 B. 电流成为原来的一半 D.电流成为原来的四分之一 C. :C D. 2. 10kWh电能可供“220V、100W”的灯泡正常发光( )h。 E. 90 B.100 C.200 D.250 ...