He didn't to do .
A:wanted;something
B:want;anything
C:wanted;anything
D:want;something
Are there circles in the picture?
①用一个完好的小灯替换R2后,小灯____ (选填“一定发光”、“一定不发光”或“可能发光”).
②电路中可能存在的故障是____.(请选填相应故障前的字母.A:R1断路;B:R1短路;C:R2断路;D:R2短路;E:R1、R2都断路;F:R1、R2都短路;G:R1断路同时R2短路;H:R1短路同时R2断路.)
A,B,C是三个不同规格的灯泡,按图所示方式连接恰好能正常发光,已知电源的电动势为E,内电阻为r,将滑动变阻器的滑片P向左移动少许,设灯泡不会烧坏,则( )
当老师的年龄是学生这么大时,学生刚3岁;当学生是老师这么大时,老师39岁.老师今年( )岁.