问题 选择题

竖直放置的一对平行金属板的左极板上用绝缘线悬挂了一个带正电的小球,将平行金属板按图所示的电路图连接,绝缘线与左极板的夹角为θ.当滑动变阻器R的滑片分别在a、b位置时,电流表的稳定示数分别为I1、I2,夹角分别为θ1、θ2,则(  )

A.θ1<θ2,I1<I2

B.θ1>θ2,I1>I2

C.θ12,I1=I2

D.θ1<θ2,I1=I2

答案

当滑动变阻器R的滑片分别在a、b位置时,根据串联电路的特点可知,变阻器左边部分分担的电压增大,电容器板间电压增大,板间场强增大,小球所受的电场力增大,则θ1<θ2.而变阻器接入电路的电阻不变,根据欧姆定律得知,电路中的电流不变,即有I1=I2

故选D

填空题
阅读理解

阅读理解。

     People who have lost the ability to understand or use words due to brain damage are called aphasics (失语

症患者). Such patients can be extremely good at something else. From the changing expressions on speakers'

faces and the tones of their voices, they can tell lies from truths.

     Doctors studying the human brain have given a number of examples of this amazing power of aphasics.

Some have even compared this power to that of a dog with an ability to find out the drugs hidden in the

baggage.

     Recently, scientists carried out tests to see if all that was said about aphasics was true. They studied a mixed

group of people. Some were normal; others were aphasics. It was proved that the aphasics were far ahead of

the normal people in recognizing false speeches-in most cases, the normal people were fooled by words, but

the aphasics were not.

     Some years ago, Dr. Oliver Sacks wrote in his book about his experiences with aphasics. He mentioned a

particular case in a hospital. Some aphasics were watching the president giving a speech on TV. Since the

president had been an actor earlier, making a good speech was no problem for him. He was trying to put his

feelings into every word of his speech.

     But his way of speaking had the opposite effect on the patients. They didn't seem to believe him. Instead,

they burst into laughter. The aphasics knew that the president did not mean a word of what he was saying.

He was lying!

     Many doctors see aphasics as people who are not completely normal because they lack the ability to

understand words. However, according to Dr. Sacks, they are more gifted than normal people. Normal people

may get carried away by words. Aphasics seem to understand human expressions better, though they cannot

understand words.

1. What is so surprising about aphasics?

A. They can fool other people.

B. They can find out the hidden drugs.

C. They can understand language better.

D. They can tell whether people are lying.

2. How did the scientists study aphasics?

A. By asking them to watch TV together.

B. By organizing them into acting groups.

C. By comparing them with normal people.

D. By giving them chances to speak on TV.

3. What do we learn from this text?

A. What ones says reflects how one feels.

B. Aphasics have richer feelings than others.

C. Normal people often tell lies in their speeches.

D. People poor at one thing can be good at another.