题干

如图所示,粗糙水平桌面上有一质量为m的铜质矩形线圈,当一竖直放置的条形磁铁从线圈中线AB正上方等高经过时,若线圈始终不动,则关于线圈受到的支持力FN及在水平方向运动趋势的正确判断是(  )

A:FN先小于mg后大于mg,运动趋势向左

B:FN先大于mg后小于mg,运动趋势向左

C:FN先小于mg后大于mg,运动趋势向右

D:FN先大于mg后小于mg,运动趋势向右

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D

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    The BBC was founded in 1922, including radio and television services. It is based at Broadcasting House in London.

    The BBC is controlled by some governors chosen by the government, but these people have freedom and the government can't interfere(干扰). That is, the BBC is supposed not to be the mouthpiece(代言人)of the government. It has to be as fair as possible in giving radio and television time to, for example, political parties and religious groups.

    There is a kind of interesting service in British­rental services. Many people prefer to rent their television sets instead of buying them.

    The rent for a black and white set is about 80 pence a week. The rent of a color set is more than twice that of a black and white set. If the sets go wrong, people can have them repaired free of charge or replaced immediately.

    Everyone has to buy a yearly license, since there is no advertising on BBC radio or television. It is from the sale of licenses that the BBC gets most of its money. A license for a black and white set costs 8 pounds, and for a color set 18 pounds a year.

    There are four special radio channels, which broadcast different kinds of programmes. Radio 1 is mainly pop music. Radio 2 deals with light music, sports and other programmes. Radio 3 broadcasts serious music, talks on serious subjects, etc. News broadcasts are mainly given by Radio 4.

    There are special programmes for Northern Ireland, Scotland, Wales, and certain parts of England. It also broadcasts programmes about Britain — in many different languages as well as in English to all parts of the world.