图中所示的电路中,电阻R1的阻值为20Ω。闭合开关S,电流表A1的示数为1.5A,电流表A2的示数为0.6A,求:(1)电源电压;(2)电阻R2的阻值;(3)电路消耗的总功率
解:由电路图知,两电阻R1与R2并联接在电源两端,电流表A1测量干路电流即流过R1、R2的总电流,电流表A2测量流过R2的电流.(1)在并联电路中,干路电流等于各支路电流之和,流过电阻R1的电流
下列说法中正确的个数有( )
①两点之间的所有连线中,线段最短;
②过一点有且只有一条直线与已知直线垂直;
③平行于同一直线的两条直线互相平行;
④直线外一点到这条直线的垂线段叫做点到直线的距离.
⑴Can I play football with you? ____
⑵What are you doing? ____
⑶Where is your mother? ____
⑷Is Oliver reading in the living room? ____
⑸Whose English book is this? ____
A. She is in the kitchen.
B. It's hers.
C. Of course.
D. I'm listening to music.
E. Yes, he is.