如图14所示,边长为L、电阻为R的正方形闭合线圈置于磁感应强度为B的匀强磁场中,

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问题:

如图14所示,边长为L、电阻为R的正方形闭合线圈置于磁感应强度为B的匀强磁场中,线圈平面与磁场方向垂直.用力将线圈分别以v1v2匀速拉出磁场,比较两个过程,以下说法正确的是(  )

①若v1>v2,通过线圈导线横截面的电荷量q1>q2 ②若v1<v2,拉力的冲量I1<I2 ③若v1<v2,拉力的功率P1<P2 ④若v1>v2,产生的热量Q1>Q2

图14

A.①③

B.②③

C.②④

D.③④

考点:电磁感应现象中的切割类问题
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按照( ),可以将债券分为政府债券、金融债券、企业债券和公司债券。

A.发行主体
B.发行方式
C.发行目的
D.发行地区

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实现运行时的多态性要使用( )。

A.重载函数

B.析构函数

C.构造函数

D.虚函数

题型:选择题

One day a rich woman lost her purse with a lot of money in it. So she made a (1) , "If anybody finds my purse and (2) it to me, I’ll give half the money to him."A poor man (3) the purse near a shop. He sent it back to the woman, but the rich woman (4) . "There was an expensive ring in my purse besides money," said the woman, "I won’t give you half the money in my purse until you return it to me." "But I’ve never seen an expensive ring in (5) purse," said the man.They began to quarrel. The man became (6) and took her to a judge. (7) the judge heard what had happened to them, he said to the woman, "I’m sure that you have lost a purse, and there is an expensive ring in it. But there is (8) a lot of money in this purse. So I don’t think it’s yours. (9) some time. Maybe somebody will give your purse back."Then the judge (10) to the man and said, "Take the purse home. If the owner doesn’t come to get it back in two days, it will be yours.

第(7)空应选择()

A.Before

B.Though

C.After

D.If

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HIS涉及了多种学科,但不包括

A.计算机
B.照片冲洗
C.医学管理
D.网络通讯
E.软件开发

题型:选择题

河水较浅的河床受到冲刷后可采用什么方法来进行防护?

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