如图,条形磁铁平放于水平桌面上,在它的正中央上方固定一根直导线,导线与磁场垂直,

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问题:

如图,条形磁铁平放于水平桌面上,在它的正中央上方固定一根直导线,导线与磁场垂直,现给导线中通以垂直于纸面向外的电流,下列说法正确的是

[ ]

A.磁铁对桌面的压力减小

B.磁铁对桌面的压力增大

C.磁铁对桌面的压力不变  

D.以上说法都不可能

考点:磁场对通电导线的作用:安培力、左手定则
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珍稀植物一般是指由于                           而处于灭绝边缘的植物。

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通常所说的血型是指

A.红细胞膜上的受体类型

B.红细胞膜上凝集原的类型

C.红细胞膜上凝集素的类型

D.血浆中凝集原的类型

E.血浆中抗体的类型

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几何形状误差包括宏观几何形状误差,微观几何形状误差和()。

A、表面波度;

B、表面粗糙度;

C、表面不平度

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《建设工程监理规范》(GB/T50319-2013)规定,工程监理单位调换()时,应征得建设单位书面同意。

A.总监理工程师

B.专业监理工程师

C.土建监理员

D.监理工程师

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(A)

Linda Evans was my best friend—like the sister I never had. We did everything together: piano lessons, movies, swimming, and horseback riding.

When I was 13, my family moved away. Linda and I kept in touch through letters, and we saw each other on special time—like my wedding and Linda’s. Soon we were busy with children and moving to new homes, and we wrote less often. One day a card that I sent came back, stamped "Address Unknown." I had no idea how to find Linda.

Over the years, I missed Linda very much. I wanted to share happiness of my children and then grandchildren. And I needed to share my sadness when my brother and then mother died. There was an empty place in my heart that only a friend like Linda could fill.

One day I was reading a newspaper when I noticed a photo of a young woman who looked very much like Linda and whose last name was Wagman—Linda’s married name. "There must be thousands of Wagmans," I thought, but I still wrote to her.

She called as soon as she got my letter. "Mrs. Tobin!" she said excitedly, "Linda Evans Wagman is my mother."

Minutes later I heard a voice that I knew very much, even after 40 years, laughed and cried and caught up on each other’s lives. Now the empty place in my heart is filled. And there’s one thing that Linda and I know for sure: We won’t lose each other again!

There was an empty place in the writer’s heart because she()

A.was in trouble

B.didn’t know Linda’s address

C.received the card that she sent

D.didn’t have a friend like Linda to share her happiness or sadness

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