一个量程为0～300μA的电流表，内阻为1000Ω，再给它串联一个99000Ω的电阻，将它改装成电压表，改装后电压表的量程为______V，用它来测量一段电路两端的电压时，表盘指针如图，这段电路两端的电压是______V．
改装后的电压表的量程为：U=Ig（R+Rg）=300×10-6×（1000+99000）=30V；
由图所示电压表可知，其分度值为1V，示数为23.0V．
故答案为：30；23.0．
| 阅读理解。 |
| One afternoon when the lessons were over, Peter and Paul did not go home. They stayed at school to help their teacher. They worked for an hour. When the boys reached home, it was seven o'clock. It was dark outside, but there was light inside their home and the door was open. "Who can it be?" said Peter. "Mother and father have gone to do some shopping. They won't be home until 8 o'clock." When the man saw Peter, he smiled and said, "Come in ! You don't know me, but I am your father's friend. He asked me to get some money for him." The man did not see Paul. Peter went inside and began talking to the man, but Paul did not. He quickly but quietly went away to call a policeman. The policeman came and caught him. |
| 1. Peter and Paul stayed behind after school____. A. until the school was over B. until 7 o'clock C. until 8 o'clock 2. Their home was bright because____. A. it was still early B. there was light C. it was dark outside 3. Peter and Paul____. A. were happy to see the man B. were afraid of the man C. tried to catch the man 4. Paul called____ to catch the man . A. their teacher B. their mother C. a policeman 5. From the story, we know____. A. the man inside Paul's home was a thief B. Peter called the policeman C. Their parents wend shopping, but they didn't take enough money with them. |