问题 多选题

如图所示是用电子射线管演示带电粒子在磁场中受洛仑兹力的实验装置,图中虚线是带电粒子的运动轨迹,那么下列关于此装置的说法正确的有(  )

A.A端接的是高压直流电源的正极

B.A端接的是高压直流电源的负极

C.C端是蹄形磁铁的N极

D.C端是蹄形磁铁的S极

答案

A、由图可知,电子是从A端射出,则A端是高压直流电源的负极.故A错误;

B、由图可知,电子是从A端射出,则A端是高压直流电源的负极.故B正确;

C、电子是从A向B运动,且洛伦兹力向下,则由左手定则可得磁场方向由C向D.故C正确;

D、电子是从A向B运动,且洛伦兹力向下,则由左手定则可得磁场方向由C向D.故D错误;

故选:BC

阅读理解

There are still many things that Peter Cooke would like to try his hand at- paper – making and feather – work are on his list. For the moment though, he will stick to the skill he has been delighted to perfect over the past ten years ;making delicate and unusual objects out of shells.

As he leads me round his apartment showing me his work, he points to a pair of shell-covered ornaments(装饰品) above a fireplace. ‘I shan’t be at all bothered if people don’t buy them because I have got so used to them, and to me they’re adorable. I never meant to sell my work commercially. Some friends came to see me about five years ago and said, “You must have an exhibition-people ought to see these. We’ll talk to a man who owns an art gallery”.’ The result was an exhibition in London, at which 70 percent of the objects were sold. His second exhibition opened at the gallery yesterday. Considering the enormous prices the pieces command-around £2,000 for the ornaments-an empty space above the fireplace would seem a small sacrifice for Cooke to make.

“I do wish, though,” says Cooke, ‘that I’d taken this up a lot earlier, because then I would have been able to produce really wonderful things-at least the potential would have been there. Although the ideas are still there and I’m doing the best I can now, I’m more limited physically than I was when I started. Still, the work that he has managed to produce is a long way from the common shell constructions that can be found in seaside shops. ‘I have a miniature(微型的)mind’ he says, and this has resulted in boxes covered in thousands of tiny shells, little shaded pictures made from shells and baskets of astonishingly realistic flowers.

Cooke’s quest for beautiful, and especially tiny, shells has taken him further than his Norfolk shore: to France, Thailand, Mexico, South Africa and the Philippines, to name but a few of the beaches where he has lain on his stomach and looked for beauties to bring home.

67.What does the reader learn about Peter Cooke in the first paragraph?

A.He has produced hand-made objects in different materials.

B.He hopes to work with other materials in the future.

C.He has written about his love of making shell objects.

D.He was praised for his shell objects many years ago.

68.When looking round his apartment, the wrier__________.

A.is attracted by Cooke’s personality

B.realizes he doesn’t like Cooke’s work at all

C.feels uncertain about giving Cooke his opinion

D.senses that Cooke wants his products to be admired

69.The ‘small sacrifice’ in Paragraph 2 refers to _________.

A.the loss of Cooke’s ornaments

B.the display of Cooke’s ornaments

C.the cost of keeping Cooke’s ornaments

D.the space required to store Cooke’s ornaments

70.What does Cooke regret about his work?

A.He is not as famous as he should have been.

B.He makes less money than he should make.

C.He is less imaginative than he used to be.

D.He is not as skillful as he used to be.

单项选择题