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问题 问答题

A如图所示，在磁极间的水平磁场中，有一水平放置的导体AC，它的方向与磁方向垂直，已知磁场的磁感应强度B=0.04T，导体单位长度的质量为0.1kg/m．为使导体悬在空中平衡，导体中应通多大的电流和方向？

答案

导线受重力与安培力平衡有：

mg=BIl

I=

mg
BL
=
0.1×10
0.04
=25A

方向C→A 

答：为使导体悬在空中平衡，导体中应通25安的电流，方向C→A

改错题

英语课上,老师要求同桌同学相互修改作文。假设以下短文为你同桌所写，请你对其进行修改。文中共有10处错误。错误涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏词符号（∧），并在此符号下面写出该加的词。

删除： 把多余的词用斜线（\）划掉。

修改： 在错的词下划一横线，并在该词下面写出修改后的词。

注意： 1．每处错误及其修改均仅限一词。 

2．只允许修改10处,多者(从第11处起)不计分。

I go abroad for further studies half a year ago. I received a lot of present. All were wrapped in color paper. Among them was two presents which really interested in me. My sister bought me the book with color pictures about body language and with words about customs of differently countries in it. My brother gave me a note saying, “My present for you has been put in my bedroom.” While I hurried into my bedroom, I found a box in it. Open the box, I found a pocket computer. I was very glad. I understood these two presents would be great help to me in improving my English.
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单项选择题

接种麻疹疫苗的常见反应为（）

A.发热

B.皮疹

C.嗜睡

D.局部红肿

E.轻微腹泻
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