问题 选择题

实验测得小灯泡L、定值电阻R的电流与两端电压的关系如图所示,则下列计算正确的是

A.若将它们并联后接入1.5V的电源,则通过干路的电流是0.32A

B.若将它们并联后接入1.5V的电源,则整个并联电路消耗的总功率为0.21W

C.若将它们串联后接入4.0V的电源,则小灯泡消耗的电功率是0.2W

D.若将它们串联后接入电压为U的电源,当电路中电流为0.2A时,定值电阻R与小灯泡L的电阻比值为2:3

答案

答案:C

本题考查的是欧姆定律的应用,并联电路的电流规律,电功率的计算。

AB、若将它们并联后接入1.5V的电源,由图知,IL=0.25A,IR=0.1A,则干路电流I=IL+IR=0.25A+0.1A=0.35A,整个并联电路消耗的总功率P=UI=1.5V×0.35A=0.525W,故AB都错;

C、若将它们串联后接入4.0V的电源时,因串联电路各处的电流相等,且串联电路的总电压等于各部分电路两端电压之和,所以在图象中,只有当电流为0.2A时,它们各自对应的电压之和才等于4V,当电流为0.2A时,灯泡的电压为1.0V,所以灯泡的电功率为P=UI=1.0V×0.2A=0.2W,故C正确;

D、由图知,当通过的电流为0.2A时,加在灯两端的电压为1V,电阻两端的电压为3V,所以电阻之比为1:3,故D错。故选C

阅读理解

BEIJING, Nov. 30 – The Bird’s Nest may have been built for last year’s Summer Games but Beijing’s Olympic stadium will soon be aiming at fans of winter sports.

As temperatures have begun to drop in recent weeks, so too has the number of visitors to the 80,000-seater venue, which cost 3.6 billion yuan ($527 million) to build.

And, fearing another harsh (寒冷的) winter, National Stadium Co Ltd, which owns the Bird’s Nest, yesterday planed to spend 50 million yuan on a “snow festival”.  

From Dec 19, visitors will be able to pay 120 yuan to enjoy skiing and snowboarding, among other things, on its newly constructed slopes.

The stadium owners expect to attract more than 20,000 visitors a day – twice as many as it currently does – during the two-month festival, which will include events for both the Western and Chinese new years.

Officials revealed it would take just 5,000 visitors a day to cover the costs of the project.

“It’s not a bad idea. You can ski on man-made snow in Dubai, so why not here?” said Heiko Grasse, a tourist from Germany, yesterday.

Famous outdoor equipment makers and local brands are in talks over sponsorship for the event, the Bird’s Nest owners said yesterday, while the capital’s television network will also provide 500 hours of coverage.

“The Bird’s Nest will not have a cold winter again,” Wu Jingjun, the new president of National Stadium Co Ltd, told China Daily yesterday. “We will create seasonal events almost every month from now on with assistance from the government and, importantly, the public.”

Yang Cheng, a newly appointed vice-president of National Stadium Co Ltd, said the snow festival would run for five consecutive winters if successful.

60. How many people visit The Bird’s Nest a day before the “snow festival”?

A. About 80,000.   B. About 20,000.    C. About 10,000.   D. About 5,000. 

61. Which of the following is TRUE according to the text?

A. The “snow festival” will attract more visitors from China than the Western countries.

B. People aren’t allowed to visit The Bird’s Nest before Dec 19.

C. The “snow festival” would run for at least five winters.

D. More than 2.4 million yuan a day is expected to be made in the “snow festival”.

62. What does Wu Jingjun mean by saying “The Bird’s Nest will not have a cold winter again”?

A. The Bird’s Nest will be kept at high temperatures in winter.

B. Winter Olympic Games will be held in The Bird’s Nest.

C. The “snow festival” will provide many events in winter.

D. The Bird’s Nest will get much more assistance from the government.

63. Which of the following may NOT be included in the “snow festival” events?

A. A football game.  B. Skiing.  C. Snowboarding.  D. A New Year’s Party. 

问答题 简答题