如图所示,R0是一个光敏电阻,光敏电阻的阻值随光照强度的增加而减小,R是电阻箱(已调至合适阻值),它们和继电器组成自动控制电路来控制路灯,白天灯熄,夜晚灯亮。下列说法正确的是( )
A:白天流过R0的电流比夜晚小
B:给路灯供电的电源应接在b、c两端
C:白天R0两端的电压比夜晚大
D:白天,如果将电阻箱R的阻值调大,则路灯也可能变成亮
A
I'm Paul. I'm 11. Frank is my friend. He is 11,too. Frank and I 1 a schoolbag this afternoon. A pencilbox and a book 2 in it.What's in the 3?Oh,there are(有) three pens. The book is4 UFOs. Is the schoolbag yours? If (假如) you lost your schoolbag, please 5 Frank or me. My telephone number is 227-8043.Frank's is 227-8046.
完成下列作图.
(1)如图1所示,能自由转动的小磁针静止在通电螺线管的上方,请在图中括号内标出电源的正极或负极.
(2)图2是一束平行于主光轴的光线经透镜折射后的光路,请在虚线框内画出一个合适的透镜.
世界上最高的大高原是( )