问题 填空题

平行板电容器的两板带电量分别为+Q和一Q,有一个带电微粒以速度V0沿带+Q的极板板面垂直于电场方向射入电场,恰好从另一极板的边缘射出,射出时的速度为v.若带电微粒带电量为q、质量为m,不计重力的影响,可知两板间的电势差大小是______;电容器的电容是______.

答案

带电微粒穿过电场的过程中只有电场力做功,qU=

1
2
mv2-
1
2
m
v20
整理得:U=
m(v2-
v20
)
2q

根据电容 的定义式:C=

Q
U
即可计算出电容器的电容:C=
Q
U
=
2qQ
m(v2-
v20
)

故答案为:

m(v2-
v20
)
2q
C=
2qQ
m(v2-
v20
)

完形填空

任务型阅读(10分)

阅读下面短文,按要求完成下列各题。

Mom’s (4) ____

A little boy invited his mother to the first teacher-parent meeting of his elementary school. To his surprise, she said she would go. This would be the first time that his classmates and teacher met his mother. She was a beautiful woman, (1)____ there was a scar (伤疤) that covered nearly the right side of her face. The boy never asked his mom why or how she got the scar.

At the meeting, other people were impressed by the kindness and natural beauty of his mother, but the little boy felt embarrassed for his mom’s looks, and hid himself from everyone. However, he heard the conversation between his mother and his teacher.

“How did you get the scar on your face?” the teacher asked.

The mother replied, “(2)When my son was a baby, his room caught fire one day. Everyone was too afraid to get into the room, but I rushed into it. While I was running towards his bed, a beam (横梁) fell down and I placed myself over him trying to protect him. I was knocked unconscious (失去知觉的). (3)幸运的是,有人救了我们。” She touched the burned side of her face. “But I have never regretted (后悔) doing what I did,” she added.

Having heard that, the little boy was so moved that he ran towards his mother with tears in his eyes. He hugged (拥抱) her and held her right hand tightly for the rest of the day.

小题1:在(1)处填入一个适当的连词使句意完整、上下文通顺:______________________

小题2:将(2)句划线部分译成汉语:______________________________________________

小题3:将(3)句划线部分译成英语:_______________________________________________

小题4:从文中找出两个形容词,对小男孩情感的前后变化进行描述:_________________

小题5:在(4)填上一个适当的名词,补全短文的标题:____________________________

单项选择题