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问题 计算题

如图所示，宽度为L＝0.20 m的足够长的平行光滑金属导轨固定在绝缘水平面上，导轨的一端连接阻值为R=1.0Ω的电阻。导轨所在空间存在竖直向下的匀强磁场，磁感应强度大小为B="0.50" T。一根质量为m=10g的导体棒MN放在导轨上与导轨接触良好，导轨和导体棒的电阻均可忽略不计。现用一平行于导轨的拉力拉动导体棒沿导轨向右匀速运动，运动速度v="10" m/s，在运动过程中保持导体棒与导轨垂直。求：

（1）在闭合回路中产生的感应电流的大小；

（2）作用在导体棒上的拉力的大小；

答案

（1）1A（2）0.1N

题目分析：（1）E=BLv  I=E/R=1A

（2）F拉=F安=BIL=0.1N

点评：本题电磁感应知识与力平衡、欧姆定律简单的综合，比较容易．

填空题

Part 1


·Read the article below and choose the best sentence from the list on the next page to fill each of the gaps.
·For each gap (1-8) mark one letter (A-H) on the Answer Sheet.
·Do not mark any letter twice.

Ways to Save


"But I can’t save any money." It’s an excuse I hear a lot. Sometimes it’s a whine. (1) . In the past few years, it has become increasingly frequent, as more and more of us Americans make less than we spend, eating up the equity in our homes, borrowing from banks. The national savings rate is declining. (2) .
The question is: Why Why don’t Americans make saving a priority We certainly know that saving money—like eating broccoli and strengthening our core muscles—is good for us. (3) . Yoga has never been hotter. And broccoli now comes as a baby vegetable, precut and bagged, and even in purple. (4) There are three reasons for this.
One: Saving today is harder. "We’ve had an income transfer away from the middle class," says Anthony Pratkanis, a psychology professor at the University of California Santa Cruz, who specializes in financial issues. The typical household income has held largely steady around the mid-S40,000 range for a good half decade, he points out, while prices have continued to rise. (5) .
Two: Credit became too accessible. (6) . While banks at one time would not let you spend more than 36 percent of your total income on debt (including mortgage) they stretched that number to 55 percent during the housing boom: Why save when yot could get that big flat-screen TV today—just like the one the neighbors installed—and pay for it with mortgage debt that was both cheap and deductible
Three—and most intriguing: Saving is, was, and always will be no fun. "Saving money," explains Jason Zweig, author of Your Money and Your Brain, "doesn’t feel good." Think about it this way: (7) . "You can buy a pair of shoes today," says Zweig, "or have a nice retirement 20 years from now." (8) . You’re going to buy the shoes or head to the restaurant because the pleasure of getting something good today is much greater than the pleasure of getting something good years in the future—even if the reward in the future is bigger.
  • A. You can go out to dinner now or put the money into an emergency fund in case the car’s transmission goes out—someday.
  • B. For years it was simply too easy to get your hands on money to spend.
  • C. In the latter cases, we listen.
  • D. Choosing to save almost always means opting for delayed gratification instead of immediate gratification.
  • E. Yet saving for tomorrow is still a largely ignored and unappreciated skill.
  • F. Other times I detect a note of defiance.
  • G. "If you’re having to spend a disproportionate amount of income on food and gas, it’s hard to save."
  • H. And the situation seems to be getting wors
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单项选择题

安全带的金属配件上应打上（）的代号。

A、该批送检

B、生产合格证

C、制造厂
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