问题 实验题

(7分)实验室有一小灯泡,上面只标有“2.5v“的字样,小滨为了测定其额定功率,从实验室找来如下器材:电流表(0~0.6A;0~3A)、电压表(0~3V;0~15V)、滑动变阻器、电源、开关、导线若干。

(1)根据小滨的实验电路图,请你用笔画线代替导线,将实物图补充完整

(2)小滨连接完电路后,发现小灯泡微微发光,移动滑片,小灯泡亮度都不改变,请帮助小滨分析原因                                    

(3)解决上述问题后,小滨又发现他选用的电压表量程0~3v挡已损坏,而另一量程挡和其他器材均完好。为了测定小灯泡的额定功率,他想出了一个解决办法。用另一量程档和阻值为6Ω的定值电阻R0,按如下图 (甲)所示的电路进行测量,闭合开关,调节滑动变阻器使小灯泡正常发光,这时电压表、电流表的示数如图(乙)(丙)所示,电压表示数为      v,电流表示数为    A,由此可以 推断小灯泡的实际电压为     v,小灯泡的额定功率为     W

答案

(1)如图:

(2)滑动变阻器同时接了下面两个接线柱;(3)5.5V;0.5A;2.5V;1.25W

题目分析:(1)滑动变阻器的接法应是取一上一下两个接线柱,图中C接线柱已接入电路,另一个应选A或B,根据电路图,滑片向左移动时电阻减小,所以接A;

(2)小灯泡微微发光,说明电路中电流太小,电阻太大,移动滑片亮度不变,说明滑动变阻器的下面两个接线柱都接入电路了;

(3)电压表只能用0—15V量程,其示数为5.5V,电流表示数为0.5A,

R0分得的电压为:,小灯泡两端电压为:5.5V-3V=2.5V,

小灯泡的额定功率为

完形填空

第二节(共5小题,每小题2分,满分10分)

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

January 13, 2010 SHANGHAI - If Google leaves China, the country will suddenly become even more dependent on its main homegrown search engine, Baidu.com. And while that is likely to benefit the Chinese company in the near term, analysts say it could do no good to the long-term development of the Internet in China.

71   , The company has 300 million users, and it is the market in China, with a commanding 63 percent share to Google’s 33 percent, according to iResearch, a consulting firm

One reason for Baidu’s leading position is its close following the nation’s tight Internet regulations and its censorship(审查) of Internet content.   72   .

“Baidu keeps a great relationship with the government,”says an advisor at 5G, a consulting firm “If the government wants something removed, Baidu will do it immediately.   73    .”

That, under local control, might be why Google never closed the market share gap with Baidu.   

74   , while Baidu insisted that they knew what Chinese users wanted.

Now, Google is suggesting that it may follow Yahoo and Ebay and actually disappear from a country that has the world’s largest Internet population-estimated to be 338 million users.“  75   

”says Yu Yang, chief of Analysts International, a Beijing-based research firm. “As for Baidu, without competition with Google, Baidu has no motivation to create.”

A.Baidu did not comment Wednesday on Google’s announcement

B.Baidu obeyed the government’s regulations, but Google did not like to, experts say

C.On the other hand, everything with Google has to go through is headquarters(总部)

D.Baidu doesn’t become famous overnightE.Google claimed they had the better technology

F.The Internet is always playing an important role in China

G.The whole industry will become worse           

填空题