问题 问答题

如图所示四个实验都是为了研究某个物理性质或规律的.

(1)甲图中,当金属夹从电阻丝上的某点,沿电阻丝向右移动的过程中,小灯泡亮度逐渐变暗.这表明______;

(2)乙图中,敲击右边的音叉,左边完全相同的音叉发生振动把泡沫塑料球弹起,这个现象说明______.

(3)丙图中,迅速下压活塞,棉花着起来,说明______.

(4)丁图中,接触面磨平的两块铅,用力压紧可以使它们结合在一起,这说明______.

答案

(1)当金属夹从电阻丝的某点,沿电阻丝向右移动的过程中,小灯泡亮度逐渐变暗.同一段电阻丝,材料和横截面积一样,只有长度影响其电阻了.

(2)由于空气能传播声音,敲击右边的音叉,声音经空气传到左边的音叉,使左边音叉振动,幷把小球弹起.

(3)通过压缩活塞对空气做功,气体内能增加,温度升高,达到棉花着火点,使棉花燃烧.

(4)把接触面磨平,使两个铅块的距离接近分子间引力发生作用的距离,两个铅块就会结合在一起,两个铅块的分子之间就存在着引力.

故答案为:(1)材料横截面积一定的电阻丝(或这段电阻丝),长度越长电阻越大;

(2)空气可以传声;

(3)压缩气体做功,气体的内能增加温度升高;

(4)分子之间存在引力.

填空题
单项选择题

In old days, when a glimpse of stocking was looked upon as something far too shocking to distract the serious work of an office, secretaries were men.

Then came the first World War and the male secretaries were replaced by women. A man’s secretary became his personal servant, charged with remembering his wife’s birthday and buying her presents; taking his suits to the dry cleaners; telling lies on the telephone to keep people he did not wish to speak to at bay and, of course, typing and filing and taking shorthand.

Now all this may be changing again. The microchip and high technology is sweeping the British office, taking with it much of the routine clerical work that secretaries did.

"Once office technology takes over generally, the status of the job will rise again because it will involve only the high-powered work-and then men will want to do it again."

That was said by one of the executives(male) of one of the biggest secretarial agencies in this country. What he has predicted is already under way in the US. One girl described to me a recent temporary job placing men in secretarial jobs in San Francisco. She noted that all the men she dealt with appeared to be gay so possibly that is just a new twist to the old story.

Over here, though, there are men coming onto the job market as secretaries. Classically, girls have learned shorthand and typing and gone into a company to seek their fortune from the bottom——and that’s what happened to John Bowman. Although he joined a national grocery chain as secretary to its first woman senior manager, he has since been promoted to an administration job.

"I filled in the application form and said I could do audio/typing, and in fact I was the only applicant. The girls were reluctant to work for this young, glamorous new woman with all this power in the firm. "

"I did typing at school, and then a commercial course. I just thought it would be useful finding a job. I never got any funny treatment from the girls, though I admit I’ve never met another male secretary. But then I joined the Post Office as a clerk and carelessly played with the typewriter, and wrote letters, and thought that after all secretaries were getting a good £1,000 a year more than clerks like me. There was a shortage at that time, you see. "

"It was simpler working for a woman than for a man. I found she made decisions, she told everybody what she thought, and there was none of that stuff’ ring this number for me dear, which men go in for."

"Don’t forget, we were a team—that’s how I about it—not boss and servant but two people doing different things for the same purpose."

Once high technology has made the job of secretary less routine, will there be male takeover Men should beware of thinking that they can walk right into the better jobs. There are a lot of women secretaries who will do the job as well as they because they are as efficient and well trained to cope with word processors and computers, and men.

A secretary in the future will()

A. be better paid

B. have less work to do

C. have higher status

D. have more work to do