_________ he was very tired, he continued working in his office.
A:Since
B:Although
C:As soon as
D:Because
电功率为40W的灯泡正常连续工作25h,消耗的电能是____J。 1kW•h可供25W的灯泡正常发光____小时。
如图所示,有一匀强磁场,磁感应强度B=2T,有一段长L=2m的导线垂直磁场方向放置,当导线中通以I=0.5A的水平向右的电流时,