问题 选择题

如图,在水平面(纸面)内有三根相同的均匀金属棒ab、Ac和MN其中ab、ac在a点接触,构成“v”字型导轨。空间存在垂直于纸面的均匀碰场。用力使MN向右匀速运动,从图示位置开始计时.运动中MN始终与bac的平分线垂直且和导轨保持良好接触。下列关于回路中电流i与时间t的关系图线.可能正确的是

A.

B.

C.

D.

答案

A

用力使MN向右匀速运动,在磁场中切割磁感线产生感应电动势。设∠bac=θ,根据法拉第电磁感应律有,。设金属棒单位长度电阻为R,根据闭合电路欧姆定律有,所以A选项正确。

单项选择题
单项选择题

After winning a big game, athletes are often asked how they feel. Usually athletes say how (1) it is to win this big game. On the contrary, the fact is that losing a big game, or in my case, all the games, can be even harder.

From the spectators’ point of view, last year’s basketball (2) for my high school team was nothing (3) of an embarrassment. And (4) 0 and 20 is certainly nothing to be proud of, that season had a bigger impact on me than any other. As a team captain, I knew it probably wouldn’t be the (5) year, but did I ever think we would lose every game Of course not. Since six of our top players had graduated, it was clear that we were a (n) (6) team who would struggle. The struggle began earlier than expected, (7) , as our team center was suspended (禁赛) for the season, and two key members decided to (8) for some reason. At this point, dropping out probably passed through every player’s mind, but in the end, we all stuck if out, (9) to work still harder.

Then there came a time when even our (10) and given up on us. Personally, I felt like it was (11) worthwhile giving my all. I thought, if even the coach doesn’t believe in us, why should I But just as my hope began to (12) , a teammate called a meeting. He said," Nobody thinks we are going to win, but, as teammates and friends, we (13) it to each other to go all out every game. "

It was that moment that (14) me how to be a leader. It hit me that I certainly didn’t (15) the role. As a leader you can never quit (16) the team who looks up to you. It is one (17) to be named captain, feel great and go through the motions, but it is quite another to be a real captain and make sure everyone realizes their full (18) all the time.

I am sure it is great to go through without losing and bringing home awards. But in all honesty, I (19) the fact that my team lost every game last year. It may not help me to become a better basketball player, but it already has made me a better leader, and (20)

5().

A.most interesting

B.dullest

C.most difficult

D.easiest