问题 选择题

如右图所示电路,闭合开关后,将滑动变阻器的滑片p 由a 端向b 端滑动过程中,图中电压表和电流表的示数变化正确的是(    )

A.电压表示数不变,电流表示数变大

B.电压表示数变小,电流表示数变大

C.电压表示数不变,电流表示数变小

D.电压表示数变大,电流表示数变小

答案

答案:C

图中电压表测量的是并联电路两端的电压,当滑片p 由a 端向b 端滑动过程中,电源电压不变,因此电压表示数不变;图中是并联电路的两条支路,当滑片p 由a 端向b 端滑动过程中是增大了其中一条支路的电阻,也就相当于增大了整个并联电路的总电阻,而图中的电流表是测量干路中的电压的,总电压不变,总电阻变大,根据欧姆定律,电流应该变小,正确答案是C。

综合
阅读理解

阅读理解。

                                              The Loss of Innocence(纯真)

     Innocence is such a precious gift. It's explained as freedom from guilt or wrong doing. Just

imagine never having to worry about anything and having a guilt-free mind. Some people wish

to save this kind of innocence from being lost from childhood to adulthood.

     What would the world be like if innocence were never lost? One way it would benefit

humanity is the lack of hatred (仇恨) among the world. During youth, there may be an occasional

argument, even a little physical fight, but nothing like firing a handgun at a fellow human being.

And children are blind towards the racial differences of others. A kid will hang out with any

other kid. It is the lack of innocence and the ignorance we learn from adults that influence

children otherwise. Another benefit is the constant desire for fun and adventure. With very little

if any time at all for fun, the adventurous mind is lost in time with the responsibilities placed upon

adults. If innocence were kept alive, these ambitions would never depart from our lives.

     However, other people actually hate the idea of innocence lasting for ever. They feel that the

lack of organization and mental power of those with innocence would cause extremely destructive

consequences to society in general. A large number of individuals would never have the urge to

learn, work, and act upon the necessary needs for humanity to survive. Without a proper

education which is usually provided by those who no longer live in a world of innocence, people

would not have the desire to succeed, get a good job in life, or provide income for their families,

which

     would hurt the lives of children.

     The lack of a good education and career would also harm the economy. As long as

innocence is kept alive, no one would be terribly angry at the lack of effort people put out in

the workplace, resulting in a strong decline(减少) in production and quality of needed goods.

     Maybe it is wrong in wanting to save innocence. It sure is a nice thought, though. Perhaps

innocence was meant to be lost. It was god's will to make things the way they are, and there

is a good purpose for everything. All that remains to be said about innocence is to enjoy it while

it lasts.

1. The author believes that the loss of innocence in adulthood should be______.

A. avoided

B. criticized

C. accepted

D. encouraged

2. Lifelong innocence would be beneficial to society in that__________.

A. proper education would be provided

B. there would be no racial discrimination

C. there would be more happy families

D. people would realize their childhood dreams

3. According to the author, people with innocence can hurt the economy with their lack of____ .

A. motivational will

B. mental ability

C. adventurous ambitions

D. needed goods

4. Which of the following shows the structure of the passage?_____

CP:Central PointP:PointSp:(次要点)C:Conclusion