试题与答案

现有一量程为3V的电压表,内阻约为5~6 kΩ,为了较准确地测量其内电阻,在没有

题型:实验题

题目:

现有一量程为3V的电压表,内阻约为5~6 kΩ,为了较准确地测量其内电阻,在没有电流表的情况下,某同学设计了如图(a)所示的实验电路,按此电路可以测出电压表的内电阻。

(1)试根据图(a)所示的电路图,完成如图(b)所示的实物电路的连线。

(2)若电源E、滑动变阻器R2、电阻箱R1各有两组可供选择:

电源E:①电动势4.0 V,有内阻;②电动势8.0 V,有内阻

滑动变阻器R2:①最大阻值20 Ω;②最大阻值1 700Ω

电阻箱R1:①0-999.9 Ω;②0~9999.9 Ω

为了减小实验误差,电源E应选____,滑动变阻器R2应选____,电阻箱R1应选____(均填序号“①”或 “②”)。

(3)该同学在开关都断开的情况下,检查电路连接无误后,接通电路前应将滑动变阻器的滑动头P置于______端。后续必要的实验操作步骤依次是:________、________、________、________、________。最后记录R1的阻值并整理好器材。(请按合理的实验顺序,选填下列步骤前的字母)

A.闭合开关S1

B.闭合开关S2

C.断开开关S1

D.断开开关S2

E.调节R2的阻值,使电压表指针偏转到满刻度

F.调节R2的阻值,使电压表指针偏转到满刻度的一半

G.调节R1的阻值,使电压表指针偏转到满刻度的一半

H.调节R1的阻值,使电压表指针偏转到满刻度

(4)按正确的实验步骤操作完成后,如果所得的R1的阻值为5 400.0Ω,则图(a)中被测电压表V的内阻rV的测量值为____Ω,该测量值____(填“略大于”“略小于”或“等于”)实际值。

答案:

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参考答案:弯曲

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题型:阅读理解

Almost everyone is afraid of something --- snakes, heights, public speaking and so on.

It is normal and can even be helpful to experience fear sometimes. In dangerous situations, fear can keep our bodies alert (警醒的) so that we can act quickly to protect ourselves.

But for some people, fear develops into a “phobia”, which is a strong and unreasonable fear of something. For example, the majority of us feel a little scared when looking down from a tall building. But people with height phobia may have trouble breathing, feel dizzy or turn down a great job just because the company is on the 20th floor.

Phobias can prevent you from living a normal life. “People with spider phobia would stay out of their home or dormitory room for days if they thought a spider was present,” Katherina Hauner, a researcher at Northwestern University, US, told ABC news. This is why scientists have been trying to find a cure for this disease.

Since fear comes from experience --- from what we are told, what we see others experience and what happens to us --- some scientists think if they can “rewrite” these unpleasant memories, they might be able to help people overcome their phobias.

In a study by Hauner and other scientists, participants with spider phobia were asked to first touch a spider with a paintbrush. Seeing that it was not actually dangerous, they then tried touching it while wearing a glove. Finally, they could hold it with their hands.

Certain medicine has also been found to be helpful. Back in 2010, researchers at the University of Hiroshima, Japan, injected (注射) a special medicine into a fish --- who was afraid of light --- to turn off the fear center in its brain. From then on, the fish no longer feared light.

While the search for solutions to phobias is making great progress, it’s an open question whether getting rid of fear is good. Some people want to use these methods to make soldiers fight harder in wars by taking away their sense of fear. Dave Smithson of the charity Anxiety UK thinks that’s a bad idea. “It’s fear that prevents us from doing crazy things,” he says. “There’s a name for people who don’t have fear of consequences: psychopaths (精神变态者).

小题1:The main point of the article is to ___________.

A.show us what kind of role fear plays in our lives

B.discuss if it is good to try to get rid of fear

C.inform us of fear and phobia

D.discuss scientific studies related to fear小题2:How does the writer make the meaning of “phobia” clear?

A.By making comparisons.

B.By giving examples.

C.By giving data in numbers.

D.By giving descriptions.小题3:Which of the following shows the progress scientists have made in finding solutions to phobia?

A.New medicine can shut off fear centers in animal brains whenever needed.

B.They can use phobias to keep our bodies alert so that we can protect ourselves.

C.They can now reduce the pain which is connected with phobia.

D.They have succeeded in helping some people ignore memories related to phobia.小题4:Which of the following would Dave Smithson probably agree with?

A.There is nothing to fear except fear itself.

B.We should not let fear affect our decisions.

C.Fear is not a completely bad thing.

D.Without fear, everyone would be brave.

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