问题 选择题

如图所示,一个不带电的表面绝缘的导体P正在向带正电的小球Q缓慢靠近,但不接触,也没有发生放电现象,则下列说法中正确的是(      )

A.B端的感应电荷为负电荷

B.导体内场强越来越大

C.导体上的感应电荷在C点产生的场强始终大于在B点产生的场强

D.C、B两点的电势始终相同

答案

CD

题目分析:导体P处在正电荷的电场中,由于静电感应现象,导体的右端B要感应出正电荷,在导体的左端C会出现负电荷,故A错误.处于静电平衡的导体内场强为0,故B错误.在C点和B点的场强由导体上的感应电荷和正电的小球Q共同叠加产生,并且为0,带正电的小球Q在C点的场强大于B点的场强,所以导体上的感应电荷在C点产生的场强始终大于在B点产生的场强,故C正确.处于静电平衡的导体是等势体,C、B两点的电势始终相同,故D正确.故本题选CD.

单项选择题 A1型题
单项选择题

It was a ruling that had consumers seething with anger and many a free trader crying foul. On November 20th the European Court of Justice decided that Tesco, a British supermarket chain, should not be allowed to import jeans made by America’s Levi Strauss from outside the European Union and sell them at cut-rate prices without getting permission first from the jeans maker. Ironically, the ruling is based on an EU trademark directive that was designed to protect local, not American, manufacturers from price dumping. The idea is that any brand-owning firm should be allowed to position its goods and segment its markets as it sees fit: Levi’s jeans, just like Gucci handbags, must be allowed to be expensive.

Levi Strauss persuaded the court that, by selling its jeans cheaply alongside soap powder and bananas, Tesco was destroying the image and so the value of its brands—which could only lead to less innovation and, in the long run, would reduce consumer choice. Consumer groups and Tesco say that Levi’s case is specious. The supermarket argues that it was just arbitraging the price differential between Levi’s jeans sold in America and Europe—a service performed a million times a day in financial markets, and one that has led to real benefits for consumers. Tesco has been selling some 15,000 pairs of Levi’s jeans a week, for about half the price they command in specialist stores approved by Levi Strauss. Christine Cross, Tesco’s head of global non-food sourcing, says the ruling risks "creating a Fortress Europe with a vengeance".

The debate will rage on, and has implications well beyond casual clothes (Levi Strauss was joined in its lawsuit by Zino Davidoff, a perfume maker). The question at its heart is not whether brands need to control how they are sold to protect their image, but whether it is the job of the courts to help them do this. Gucci, an Italian clothes label whose image was being destroyed by loose licensing and over-exposure in discount stores, saved itself not by resorting to the courts but by ending contracts with third-party suppliers, controlling its distribution better and opening its own stores. It is now hard to find cut-price Gucci anywhere.

Brand experts argue that Levi Strauss, which has been losing market share to hipper rivals such as Diesel, is no longer p enough to command premium prices. Left to market forces, so-so brands such as Levi’s might well fade away and be replaced by fresher labels. With the courts protecting its prices, Levi Strauss may hang on for longer. But no court can help to make it a great brand again.

The word "specious" (Line 4, Paragraph 2) in the context probably means()

A. responsible for oneself

B. having too many doubts

C. not as it seems to be

D. raising misunderstanding