问题 多选题

如图(a)所示,AB是某电场中的一条电场线,若有一电子以某一初速度且仅在电场力的作用下,沿AB由点A运动到点B,所经位置的电势随距A点的距离变化的规律如图(b)所示.以下说法正确的是(  )

A.A、B两点的电场强度EA>EB

B.电子在A、B两点的速度vA<vB

C.A、B两点的电势φA>φB

D.电子在A,B两点的电势能EPA<EPB

答案

A、φ-x图象的斜率大小等于电场强度,由几何知识得知,图象的斜率减小,则从A到点B场强减小,则有EA>EB.故A正确.

B、D由图看出,电势逐渐降低,可判断出电场线的方向从A到B,在移动过程中,电场力做负功,电子的动能减小,速度减小,而电子的电势能增大.即有vA>vB,EPA<EPB.故B错误,D正确.

C、电场线的方向从A到B,则A、B两点的电势φA>φB.故C正确.

故选ACD

阅读理解

For many years, a small percentage of homeowners have fixed solar panels (太阳能板) on their rooftops. Those panels collect some of the sun’s energy and either change it into electricity or use it to heat water. Until recently, the panels were too expensive for average homeowners, and their designs were not attractive. Thanks to new advances, however, solar panels for homes are becoming cheaper and less large and heavy. Now more homeowners are considering using them.

Stores begin to sell Solar panels

Last fall furniture retailer(零售商) IKEA began selling solar panels in its U.K. stores. IKEA has brought the DIY solar choice to the public. While shopping for furniture, shoppers could not add a box or two of solar panels to their shopping cart (购物车). IKEA is partnering with a company. The company deals with fixing and servcing of the solar panels on the roofs. So it is easy for customers to change from old energy system to solar system. If all goes well, IKEA plans to begin selling the panels in other countries soon.

Stylish solar panels

SolTech, a Swedish company, offers a really great solar-power solution. Instead of flat panels, SolTech covers the panels with a special glass tile.  And the shape of the glass tile fits traditional tiled roof designs. SolTech recently offers solar systems that heat the home’s air or water. And it also offers one solar system that produces electricity.

______________

New technology has turned windows into solar panels. SolarWindow technology enables see-through windows to produce electricity after the glass surface is added with a special coating. Amazingly, SolarWindow can produce electricity in low-light conditons and can even turn indoor, man-made light into electricity! Since buildings are getting taller and about 60 percent of an office building’s surface is covered with windows, solar window could become a very popular way for people to produce energy and save money.

Turning your home –business-into a solar-powered one is a choice that’s becoming a lot more attractive these days!

小题1:This passage mainly talks about ______.

A.fashion shows

B.life in the UK

C.a technology

D.different opinions小题2:The reason why only a few homeowners used solar panels is that they are __________.

A.cheap but heavy

B.attractive but expensive

C.light and small

D.dear and not attractive小题3:.The DIY solar choice has been brought to the public so that _______.

the IKEA stores can sell more furniture in the U.K.

it is possible to make more panels in other countries.

more people will choose to use a new energy system.

people can get solar panels for free after buying furniture.

小题4:.The best title for the fourth paragraph is __________.

A.Making new kinds of windowns

B.Turning windows into solar panels

C.Changing our homes into panels

D.Adding electricity to the windows小题5:.The author’s attitude towards solar panels is _________.

A.positive     B.negative    

D.uncertain     D.questioning

名词解释