问题 选择题
长度相等、电阻均为r的三根金属棒AB、CD、EF用导线相连,如图所示,不考虑导线电阻,此装置匀速进入匀强磁场的过程中(匀强磁场垂直纸面向里,宽度大于AE间距离),AB两端电势差u随时间变化的图象可能是(  )

A.

B.

C.

D.

答案

答案:C

阅读理解

Many people are concerned about the state of the earth in terms of its energy supplies and changing climate.The clear message broadcast by all responsible governments is that every person has a part to play.Here are some detailed instructions.

1.Prevent pollution by disposing(清理) of all your litter and waste in the correct,legal way,such as using on­street waste receptacles(容器) when you are out and about,or putting it in your domestic rubbish can when you're at home.Follow local procedures for normal waste disposal.Contact your local authority for advice on disposing of unusual waste items,such as paint and computer parts.

2.Recycle all materials that can be processed by your local authority.Place plastics,metals,paper and glass in the correct collection receptacles.Donate unwanted items to the charities that are happy to accept good condition clothing,furniture and even automobiles.

3.Look after reserves of water by making sure you turn off the tap after use and by repairing leaks(渗漏) and drips.Purchase water­efficient appliances.Take showers instead of baths.Gather rainwater for garden use and use your lawn sprinkler less often or not at all.

4.Save energy by choosing Energy Star products.Turn these off,as well as lights,when you don't need them to be on.Use air condition and heating less often.Make sure your home is insulated correctly to maintain a steady temperature.

5.Reduce the amount of the material you use.Print emails occasionally or not at all rather than printing them every time.You buy new things when you actually need them rather than on a whim(心血来潮).Organize a car pool with friends to use fuel efficiently.

In a word,we should try to use the world's resources efficiently to protect the environment.

小题1:When you have a walk in the park,you________.

A.can throw away the waste freely

B.had better take along the waste

C.can throw the waste into rubbish can

D.should put the waste in your domestic rubbish can小题2:Which can't be recycled according to the passage?

A.Metal.

B.Glass.

C.Automobiles.

D.Paint.小题3:Why should you take showers instead of baths?

A.Because it is comfortable.

B.Because it can save lots water.

C.Because it can gather water.

D.Because it is convenient to use.小题4:What's the main idea of the whole passage?

A.How to protect the environment?

B.Reduce the amount of the material you use.

C.Some instructions in energy supplies.

D.Why should each play a part in saving energy?

单项选择题