问题 选择题

如图所示,长直导线旁边同一平面内有一矩形线圈abcd,导线中通有竖直向上的电流。下列操作瞬间,能在线圈中产生沿adcba方向电流的是

A.线圈向右平动

B.线圈竖直向下平动

C.线圈以ab边为轴转动

D.线圈向左平动

答案

答案:D

题目分析:根据右手螺旋定则可得直导线右边部分产生方向为垂直纸面向里,并且越偏离导线,磁场越弱,

当线圈向右平动时,垂直向里的磁通量减小,所以产生的感应电流方向为abcda,A不符合题意

当线圈竖直向下平动时,线圈中的磁通量不变化,故不产生感应电流,,B不符合题意

当线圈以ab轴转动时,过程中产生abcda方向的电流,C不符合题意

当线圈向左平动时,垂直向里的磁通量增大,所以产生的感应电流方向为adcba,D符合题意

故选D

点评:线圈中的感应电流产生的磁场总是阻碍原磁场的变化

填空题
阅读理解

The food on the moon has come a long way from the freeze – dried bread to half – dried food. They have changed a lot in the past few years. And now US scientists want to grow vegetables in mini – greenhouses on the moon.

Scientists say they are looking forward to a time when people on the moon or even Mars will be able to eat green and fresh vegetables. Paragon Space Development Corporation has shown people what it called the first step toward growing flowers – and finally food – on the moon.

Paragon, which is a partner of NASA in experiments at the International Space Station, calls it a “Lunar Oasis (绿洲)”

This is a closed greenhouse placed in a metal box. It is designed to safely land a laboratory plant on the moon surface, and protect it while it grows.

The small greenhouse is to be sent up into space by Odyssey Moon Ltd, which takes part in the Google Lunar X Prize. This competition offers $ 20 million to any company which can send up, land and operate a lunar rover (月面车) on the moon surface.

Leaders of Paragon say future testing of the “Lunar Oasis” will be driven by Odyssey’s flight schedule, which will not happen until 2012 at the earliest.

When it is sent up, the greenhouse will have the seeds (种子) of cabbage inside it. Because they go from seed to flower in just 14 days, they can complete their life cycle in a lunar night.

“Growing plants on the Moon or Mars seems so far away, but it is important that we do this research now,” Paragon president Jane Poynter said. “It takes a long time to do a lot of research.”

小题1:What do we know about “Lunar Oasis” from the passage?

A.It is made of wood by scientists.

B.It is open for people who are on the Mars.

C.It can carry different kinds of plants to the moon.

D.It will protect plats to grow on the moon.小题2:The seeds of cabbage are chosen because they         .

A.have beautiful followers

B.can grow very quickly

C.can grow in the greenhouse

D.can grow bigger than other seeds小题3:According to the passage, Paragon Space Development Corporation      .

A.has produced food on the moon

B.is in charge of NASA in experiments

C.takes part in the Google Lunar X Prize

D.may test “Lunar Oasis” in the future小题4:What does Jane Poynter think of growing plants on other planets?

A.It is possible.

B.It can be realized easily

C.It is impossible.

D.It will come true very soon.小题5:What would be the best title for the passage?

A.Exploring the Moon and the Mars

B.Making Use of the Lunar Rover

C.Researching Fresh Food on the Moon

D.Seeking the Living Things on the Moon