问题 单项选择题

有如下程序: #include<iostream> using namespace std; int main() { int *p; *p=9; cout<<"The value at p:"<<*p; return 0; } 编译运行程序将出现的情况是( )。

A.编译时出现语法错误,不能生成可执行文件

B.运行时一定输出:The value at p:9

C.运行时一定输出:The value at p:*9

D.运行时有可能出错

答案

参考答案:D

解析: 题目程序中“int *p;”是定义了一个指针变量p,“*p=9;”是将p当前指向的指针赋为9。指针p在执行这个赋值操作前并没有初始化这个变量p,所以会有p未初始化的警告错误。

实验题

小明学会了测小灯泡的功率后,在老师的启发下,进一步思考:电流一定时,小灯泡功率跟电阻有什么关系呢?于是他利用如图所示电路,选用分别标有“1.5V 0.25A”、“2.5V 0.3A”和“3.8V 0.3A”字样的小灯泡L1、L2、L3,测出它们在电流相同时的电阻和功率,来探究小灯泡功率与电阻的关系。

(1)他将灯L1接入电路,请你用笔画线代替导线,帮他将实物电路连接完整。

  

(2)闭合开关前,滑动变阻器的滑片P应置于       (选填“A”或“B”)端。

(3)若闭合开关后,发现灯泡很亮,且调节滑动变阻器时电压表、电流表的示数均无变化,以下三个选项中不可能是电路中存在的问题的是       (选填字母序号)。

A.滑动变阻器短路    B.滑动变阻器断路    C.滑动变阻器接成了上面两个接线柱

(4)排除故障后,闭合开关,他调节滑动变阻器的滑片P,使通过灯L1的电流为0.2A,再测出L1两端的电压,此时电压表示数如图所示,为      V,然后计算出此时灯L1的电阻是      Ω,实际功率是      W;换上灯L2,闭合开关,调节滑动变阻器,使电路中电流为0.2A不变,再测出L2两端的电压,算出L2的电阻和功率;换上灯L3,闭合开关,调节滑动变阻器,使电路中电流为0.2A不变;再测出L3两端的电压,算出L3的电阻和功率。并将以上实验数据记录在表1中。

  

(5)请根据实验数据,在图中作出小灯 泡功率与电阻关系的图象。

(6)分析图象可得结论:在电流一定时,小灯泡的实际功率与电阻成      关系。

(7)小明认为:为了控制实验条件,小明每次实验要换灯泡还要调节滑动变阻器,这样的操作不够简便。对此你可以如何改进?                                             

单项选择题

Whoever said that victory has many fathers and defeat is an orphan, surely had never heard of the World Trade Organization (WTO). In the case of the hapless multilateral trade body and its long suffering representatives, the total failure of the opening meeting of the so called Millennium trade round has lots of people boasting of their roles in the violent physical struggle. Well. That’s just brilliant. They are proud of being part of a movement that wants to wreck the most important engine of economic growth, prosperity and overall global rising living standards we have--the freedom of trade and movement of people and goods between nations.

The 135-member WTO is composed of sovereign governments wishing to further this goal and ease the settlement of international trade disputes. From the sounds emanating from Seattle, though, it would now seem the WTO has now replaced the Trilateral Commission and the Freemasons as candidate No. 1 to take over the World.

Everybody has his favorite Seattle story. The city’s police chief will have plenty of time to think about his, having now resigned in disgrace over the loss of control of downtown Seattle. The Seattle business community may be more inclined to brood over theirs--the poor fools invested $ 9 million to attract the meeting to their fine city. What stands out more I would nominate the union of steel workers who were marching in protest. It’s an image that will boggle the mind for years to come.

The debate now is over just how effective this anti-globalist coalition will turn out to be. In the heat of the moment, it always looks as though the world as we know it is coming to an end. But the overwhelming likelihood is that we have not actually seen a replay of the anti Vietnam War movement, which had much clearer focus, obviously, though its consequences were far-reaching. How long, after all, can you protest against cheap imports when those same imports are all over your house

No, the real reason for the disaster in Seattle is political, and reports coming out of the meeting point to President Clinton as a major culprit. Which may be both good and bad. Taking the long view, other trade rounds have had difficult beginnings, too. It took years to get the Uruguay Round under way, which finally happened in 1986. Thankfully, we will soon be electing another president, and it should be someone whose actions match his rhetoric.

Still, it is a disgrace that the world’s greatest trading nation, i.e. the United States, is currently led by a man whose motivations are so narrowly political and egocentric that he has now wrecked any chance of entering the history books as a champion of free trade.

The statement "victory has rnany fathers and defeat is an orphan" (Para. 1) is used to introduce()

A. the victory of suffering representatives

B. the failure of WTO’s opening meeting

C. the role of international free trade

D. the dynamics of economic growth