题干

如图所示,一个边长为L的正方形导线框以速度v匀速通过宽为d(d<L)的匀强磁场,在此过程中线框中有感应电流的时间是(   )

A:2d/v

B:2L/v

C:(L-d)/v

D:(L-2d)/v

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答案(点此获取答案解析)

A

同类题2

阅读理解

    Time flies, or so they say. No matter where you are, humans are constantly measuring and checking time. Some of us are good at it—planning and doing things ahead of time—while others are always trying to beat the clock and do things at last. What about if you are behind time?

    Delay can be serious. If you were one minute late for work, would you resign? It may sound extreme to many of us, but that is exactly what occurred in the UK upper chamber of parliament, the House of Lords, in January 2018. International development minister Lord Bates arrived one minute late, and, as a result, was unable to answer a scheduled question. Instead of trying to make up for lost time, he resigned on the spot. He apologised for his discourtesy and stated that he was ashamed. His resignation, though, was not accepted by the UK prime minister.

    So, how late is too late? Many cultures take punctuality very seriously, whereas others seem to accept lagging behind as just the normal way of things. BBC employees from Latin America, Rwanda and Sri Lanka said that there are more flexible attitudes to timekeeping in their cultures. In Latin America, things may happen five minutes, 20 minutes, an hour or even two after they were planned. Whereas, in Sri Lanka, lateness is a part of the daily routine. This is because of poor infrastructure and heavy traffic conditions. In Rwanda, those who attend to deadlines with strick timekeeping are said to be “like a typical European”.

    On the other hand, German and Japanese employees mentioned a stricter adherence to time. In Japan, it is common to make an effort to arrive with time to spare for an appointment. Those who arrived at the stroke of nine to a meeting starting at 9 am would be considered late. In Germany, however, if a dinner party were to begin at eight, a person who had arrived five minutes prior, may walk around the block to make sure that they arrive at eight on the dot.

同类题5

任务型阅读

    Currently offered by some famous universities, MOOCs are attractive to people who do not have the financial resources to meet the growing costs of university education, or who do not have formal qualifications. They also allow participants to study at their own pace.

    The potential for MOOCs to deliver education is obviously vast—they could be considered as a huge step forwards in widening participation. They also have the potential to provide a unique window on universities that offer popular and valuable courses, they may attract some participants to register for formal fee-paying programmes at the same or other universities and are likely to promote new ways of on-line education.

    However, it is still very early days for MOOCs. The quality of the education provision is highly variable, with many courses offering only recordings of lectures, and delivery is particularly difficult in some special fields that require practical classes, research projects or extensive library access. Besides, wider engagement with participants requires very considerable resource. Even limited feedback or examination becomes a major task if there are several thousand students in the class.

Considering the challenges, some people argue MOOCs will soon evaporate (蒸发). But they certainly provide good opportunity for widening higher education, are a means of raising awareness of universities to audiences of tens or hundreds of thousands, and are well worthy of serious consideration.