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问题 问答题

如图巳证明电子射线管中所加的偏转电压使电子在荧光屏上发生偏移的距离：D=（ι/2d）（U2/U1）（L+ι）

式中ι为偏转电压电极的长度，d为偏转电极极板间距，U1为电子加速电压，U2为偏转电压，L为偏转电极极板到荧光屏距离．

上述结果是否正确？若正确，列式证明；若错误，求出正确结果．

答案

（1）错．因为在电场中侧移量为y=

1
2
at2=
U2l2
4dU1
．

（2）因为偏移的距离：D=

1
2
at2+L（
VY
V0
）              

而电场中的侧移量为，

1
2
at2=
1
2
（
eU2
md
） t2         

由于匀速直线运动，则有t=

l
V0
      

粒子在电场中加速运动，则有eu1=

1
2
mV02 

所以Vy=

eU2
md
l
V0
                    

因此，D=

lU2
2dU1
(L+
l
2
)

答：射线管中所加的偏转电压使电子在荧光屏上发生偏移的距离为

lU2
2dU1
(L+
l
2
)．

阅读理解

Did you watch the magic shows played by Liu Qian from Taiwan in the 2009 CCTV Spring Festival Gala（春节联欢会）? They attracted great attention and wide interests of the audience(观众) . During the gala, Liu mangaged to drop a coin into a glass which was placed upside down (倒置) and transferred a finger ring into an egg. The two magic shows were so successful that everyone is now mad about him and all want to know how to play magic tricks. “I saw the surprise on everyone’s face. It was cool, ”Liu said.

However, you may not believe that Liu didn’t go to any magic school. He just learned by himself. When Liu was seven, he saw a coin trick in a big store. At that moment Liu decided to learn magic. He worked hard at it. He practiced hard to improve his skills. Then one day he was able to put on a show for his class.

After years of hard work, now Liu is a great magician. But he isn’t satisfied with what he has got and keeps on trying every day. He may spend three years working out a new show.

小题1: Liu Qian becomes famous______.

A．because he is from Taiwan

B．for his magic shows.

C．only in Taiwan

D．when he was seven.小题2:According to the passage, we can use the following words to describe Liu Qian  EXCEPT______.

A．creative

B．hardworking

C．satisfied

D．wise.小题3: What does the underlined word “transferred”mean?

A．制作

B．进入

C．输入

D．转移
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单项选择题

股指理论价格上移－个交易成本之后的价位称为（）。

A．无套利区间的下界

B．期货理论价格

C．远期理论价格

D．无套利区间的上界
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