下列关于静电场的说法正确的是（） A．正电荷只在电场力作_爱下问搜题

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问题选择题

下列关于静电场的说法正确的是（　　）

A．正电荷只在电场力作用下，一定从高电势向低电势运动

B．在点电荷形成的电场中没有场强相等的两点，但有电势相等的两点

C．场强为零处，电势一定为零；电势为零处，场强一定为零

D．初速为零的正电荷在电场力作用下一定沿电场线运动

答案

A、正电荷只在电场力的作用下，其运动是由电场力和初速度共同决定的，如正电荷在电场中做减速运动，就是由低电势向高电势运动．故A错误．

B、场强是矢量，根据点电荷形成的电场线可知：各点的场强不同；又因为电场线与等势面垂直，且电势为标量，故在点电荷形成的电场中没有场强相等的两点，但有电势相等的很多点．故B正确．

C、电势是标量且具有相对性，与零势面的选取有关，故场强为零处，电势不一定为零；电势为零处，场强不一定为零．故C错误．

D、初速度为零的正电荷在电场力作用下其运动取决于电场力，如果电场力方向不变，一定沿直线运动，否侧沿曲线运动，并不一定沿着电场线运动．故D错误．

故选：B．

完形填空

完形填空（共20小题：每小题1.5分，满分30分）
阅读下面短文，从短文后所给各题的四个选项（A、B、C、D）中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
Several years ago, a friend of mine and her husband were invited to spend the weekend at the husband’s employer's home．My friend，Arlene，was nervous，because the boss was very 21 with a fine home，and cars that 22 more than her house.
The boss was a generous 23 , and took them to the __24__ restaurants. Arlene knew she would 25 have the opportunity to go to such places again, so she was 26 herself greatly.
They were about to 27 a good restaurant that evening when the boss stopped suddenly, looking __28__ at the road. Arlene wondered if she was supposed to __29__ him. There was nothing on the 30 except a penny.
The boss reached down and 31 the penny. He smiled, and then put it in his __32__as if he had found a great treasure. Why would a man like this pick up a single __33__? Why would he even take the time to __34__?
When they were in the restaurant she could 35 it no longer. She mentioned that her daughter had once had a coin ___36__ , and asked if the penny had some value.
A __37__ crossed the man's face as he took the penny out of

his pocket.
"Look at it," he said, "'In God We Trust'."
"In America, for those who trust in God, the name of God is holy, even on a coin.__38__ I find a coin I see those words. They can be __39__ on every single American coin,but people never seem to 40 them! For a short time, at least, I treasure each one as if it were gold."

B．applied for

单项选择题

DCS系统其核心结构可归纳为“三点一线”结构，其中一线指计算机网络，三点分别指（）。

A、现场控制站、操作员站、数据处理站

B、现场控制站、操作员站、工程师站

C、现场控制站、数据处理站、工程师站

D、数据处理站、操作员站、工程师站