在图中，标出了磁场B的方向、通电直导线中电流I的方向，以及通电_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

在图中，标出了磁场B的方向、通电直导线中电流I的方向，以及通电直导线所受磁场力F的方向，其中正确的是（　　）

A．①②

B．①④

C．①③

D．③④

答案

A、由左手定则可知，通电导线所受安培力竖直向上，故①正确；

B、由图可知，磁感应强度B与电流I平行，导线不受安培力，故②错误；

C、由左手定则可知，通电导线所受安培力竖直向下，故③正确；

D、由左手定则可知，通电导线所受安培力垂直于纸面向外，故④错误；

故选C．

完形填空

Once upon a time, there was a little boy named Rakesh, he studied and lived in a boarding school(寄宿学校). Every night he jumped over the wall and played outside. He        returned before dawn (黎明) and lay on his bed again, so no one knew that Rakesh went out at        .
One night as usual, Rakesh found         asleep. He decided to play outside again. He went into his teacher—Mrs. Green’s room        and saw her        . Then Rakesh walked out towards the wall. Near the wall, there was a ladder in the bushes, he hid it there. He         the ladders and he climbed up it , then jumped over the wall.        at that time his teacher was awake and saw him going out.
      got up and took away the        from the wall. A few hours        , Rakesh returned. In the dark, he tried to climb        from the wall. Sadly, there was no ladder, instead, Mrs. Green was standing where the ladder was and waited for him. Rakesh was very        to be punished (处罚), but to his surprise, she just helped Rakesh to get onto the ground , said, "Rakesh, at least        a warm coat with you, when you go out at night."
Mrs. Green's        made Rakesh know his own faults. He apologized (道歉) and never went out at night again. It is the        lesson that he has ever had.

C．watching TV

A．took care of

C．took a look at

填空题

我国在对外谈签税收协定时，一般比较倾向于（）范本。