问题 问答题 简答题

电动自行车用电池是如何分类的?

答案

参考答案:

从大的方面讲,电池分一次电池(电动车用它做电源已经成为历史)、二次电池和燃料电池。车用电池按电解液性质分为酸性和碱性,按外形分为方形和圆柱形,按使用性质分为移动式和固定式,按用途分为动力型、起动型和普通型,按结构分为开敞式和密封式。其中:铅酸电池又有不同形式,如从外形结构又分为高型和矮型;按酸性电解液的状态分为富液型、贫液型和胶体电解液三种,按极板的结构分为板式、卷式和管式。

目前电动车常规电池主要为铅酸电池、镍氢电池、镍锌电池,其中又以铅酸电池最普及,其余两种乃是仍然较少。主要原因是市场动作没有展开,没有形成适合电动车对路产品的规模产量,价格未能被广大用户所接受,但很快就会进入热潮。技术成功的其他三种电池——锂离子电池、锌空气电池是继镍氢、镍锌电池之后的升级产品;燃料电池价格仍高不可攀,主要原因是质子交换膜制备成本高,催化金属属于贵重物,某些技术仍然需要提高,未能大规模进入生产领域,仍需6~8年的时间才能普及。

选择题
写作题

请仔细阅读下面所给的英文信,然后给Worried写一封回信。

Dear Helpful,

I’m a middle school student and I’m in trouble. I used to like English, but now I have some difficulty in English, especially in English writing. Though I know English is a very important subject, I think now it is too difficult for me. You know I have got poor results in English tests many times because my writing is poor. I wonder why so many students like English and can get good results in English tests. I do want to be one of the best students and go to a famous university after graduation. But my English is not good enough. What should I do?

Worried

回信包含以下内容:

1. 要有自信心;

2. 多记一些惯用词组 (set phrases) 和句型结构 (sentence structures),多造句;

3. 大量阅读可以提高写作水平;          4. 多背诵一些好的短文;

5. 写日记是提高写作的好方法;          6. 要经常练习。

要求:

1.至少写出五项内容;               2.开头、结尾已给出,不计入总词数;

3.不要逐字逐条翻译,可以适当增加细节,词数100—120左右。

Dear Worried,

I have received your letter and I’m glad to give you some suggestions.

_______________________________________________________________________________

Follow your dream and you’ll find success is just around the corner!Good luck to you in your writing.