问题 选择题

关于电场中的下列说法正确的是(  )

A.某点电势高,说明该点电势能大

B.电场力做功为零,说明该运动电荷一定是沿着等势面移动的

C.若带电粒子在电场中移动时电势能减少,则电势一定降低

D.负电荷在电场中无初速度,只在电场力作用下运动电势能一定减少,同时一定是从电势低处移向电势高处

答案

A、C、电势是电场的性质,电势能是电荷的性质,与电荷的带电性有关,正电荷在电势高处电势能大,负电荷在电势低处电势能大.没有说明电荷带正电还是带负电时,某点电势高,不能说明该点电势能大;电势能减小,不能说明电势一定降低.故A、C错误.

B、电场力做功与路径无关,只取决于初末位置的电势差,根据电场力做功的表达式W=uq,电场力做功为零,只说明初末位置的电势差为零,即初末位置是等电势点,但不能说明该运动电荷一定是沿着等势面移动的.故B错误.

C、负电荷在电场中无初速度,只在电场力作用下运动,则电场力一定做正功,故电势能一定减少.负电荷在电势低处电势能大,在电势能小的地方电势高,故一定是从电势低处移向电势高.故D正确.

故选:D.

问答题
翻译题

完成句子

阅读下列各小题,根据每句后的汉语提示,用句末括号内的英语单词完成句子.

1. The boy ____________________ reading a novel that he forgot there was a large amount of

    homework remaining unfinished. (lose)

这个男孩如此入迷地看着小说,以至于都忘了还有一大堆作业没写完.

2. If all nations ____________________their energy supply sources to reduce waste a little earlier,

    things would be much better now. (seek)

如果所有的国家早一些通过寻求改变能源供应的来源来减少浪费的话,现在一切都会好很多.

3. It is not who is right but what is right ______________. (importance)

重要的不是谁是对的,而是什么是对的.4. Nothing gave the mother more pleasure than ____________________ to be useful citizens of the country. (bring)

没有什么比看见自己的孩子被培养成对祖国有用的人才更让她高兴的了.

 5. The combined working group will look into the train rearend collision(追尾事故), ____________________ the cause of accident officially and punishing some responsible persons concerned. (account)

联合工作小组将会调查火车追尾事故,来正式说明事故原因,并惩罚相关的负责人员.

6. They were about to get down the hill ________________heavily. (begin)

他们正要下山,这时天突然开始下起了大雨.

7. They urged him to go on with his story, so he had to stop ____________________the delicious

    food on the table. (stare)

他们催促他继续(讲)他的故事,因此他不得不停止盯着桌上美味的食物.

8. The rain was heavy but, ____________________, our fields were not flooded. (contrary)

尽管雨下得很大,不过和我们的担忧相反,我们的地并没有被淹没.

9. Not being able to come up with a solution to his being penniless, he had to earn his living ________________________. (work)

实在是想不出什么方法能够解决他的贫困问题,他不得不靠做服务生谋生.

10. The teacher asked ____________________the present situation, but there was really no quick

      answer to it. (do)

老师问我打算如何处理目前的状况,但是这个问题真的很难用一两句话来回答.