问题 选择题

(2009·淄博一模)如图所示,两虚线之间的空间内存在着正交或平行的匀强电场E和匀强磁场B,有一个带正电的小球(电荷量为+q,质量为m)从电磁复合场上方的某一高度处自由落下,那么,带电小球可能沿直线通过的电磁复合场是                                                (  )

答案

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在A图中刚进入复合场时,带电小球受到方向向左的电场力、向右的洛伦兹力、竖直向下的重力,在重力的作用下,小球的速度要变大,洛伦兹力也会变大,所以水平方向受力不可能总是平衡,A选项错误;B图中小球要受到向下的重力、向上的电场力、向外的洛伦兹力,小球要向外偏转,不可能沿直线通过复合场,B选项错误;C图中小球受到向下的重力、向右的洛伦兹力、沿电场方向的电场力,若这三个力的合力正好为0,则小球将沿直线通过复合场,C选项正确;D图中小球只受到向下的重力和向上的电场力,都在竖直方向上,小球可能沿直线通过复合场,D选项正确.

完形填空

任务型阅读

The people below are all trying to choose which TV programme to watch.  After the description of these people, there is information about five TV programmes A-E. Decide which programme would be most suitable for the person mentioned in questions 1-4 and then mark the correct letter (A-E) on your answer sheet. There is one extra paragraph about one programme which you do not need to use.

_________1Bella enjoys eating out but can’t afford to spend very much at the moment as she is saving for a holiday. She has never learnt how to cook, so now might be quite a good time to find out!

________2Dan is interested in taking wildlife photographs and enjoys the kind of programme which gives him a chance to see a professional photographer at work.

_________3Gina is a music teacher. Although she prefers classical music, she likes to follow the kind of music that interests the teenagers she teaches.

_________4Ron’s wife is in hospital. He wants to finds a programme suitable for his three-year-old son while he gets on with the housework and prepares a meal.

TODAYS  TELEVISION  PROGRAMME  PREVIEW

A.TV1 7:20 p.m. Find out more about Australia’s animal life. This film was made last year by one of Australia’s best-known cameramen, Dougie Bond. He spent over 200 hours filming the birds, animals and fish that inhabit this beautiful continent and for the first time brings some of these unusual animals to our TV screens.

B.TV3 9:00p.m. The popular science programme is back with the latest in technology and medicine. This week, cars that run on sunlight and the story of one baby’s fight to live.

C.TV15:15p.m. Busy parents? Bored children? Do you want something educational to entertain your children while you do something else? This popular magazine programme is for the under-fives. More music, fun, songs and games with Carla and Larry.

D.TV3 8:45p.m. If you’ve always wanted to cook, now’s your chance to learn. In the studio are two chefs who will take you through some simple recipes step by step. This is a repeat of the popular series shown last year, and available from good bookshops.E . TV3 7:40p.m. The latest new music. Pete Hogg looks at the best of the current rap, raga and new jack swing plus new video releases. This is the programme that tells you all about what’s happening on the music scene and brings you interviews with tomorrow’s young artists.

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