问题 选择题

如图所示,纸面内有一矩形导体闭合线框abcd,ab边长大于bc边长.从置于垂直纸面向里、边界为MN的匀强磁场外,线框两次匀速地完全进入磁场,两次速度大小相同,方向均垂直于MN.第一次ab边平行MN进入磁场.线框上产生的热量为Q1,通过线框导体横截面的电荷量为q1:第二次bc边平行MN进入磁场.线框上产生的热量为Q2,通过线框导体横截面的电荷量为q2,则(  )

A.Q1>Q2q1=q2

B.Q1>Q2q1>q2

C.Q1=Q2q1=q2

D.Q1=Q2q1>q2

答案

设ab和bc边长分别为lab,lbc,若假设穿过磁场区域的速度为v,

Q1=BI1Lab•Lbc=

B2
L2ab
v
R
•Lbc

q1=I1△t=

N△Φ
R
△t=
BLabLbc
R

同理可以求得:Q2=BI2Lbc•Lab=

B2
L2bc
v
R
•Lab

q2=I2△t=

N△Φ
R
△t=
BLabLbc
R

lab>lbc,由于两次“穿越”过程均为相同速率穿过,

因此:Q1>Q2,q1=q2,故A正确,BCD错误.

故选:A.

阅读理解

The International Space Station allows astronauts to live in space for extended amounts of time, enabling them to explore the outside universe and conduct many experiments. However, nothing like that exists for our oceans, and thanks to the high water pressure, ocean researchers are able to explore what lies undersea for very short periods of time.

They are therefore never able to fully explore the deep inside areas of our oceans. However, if French architect Jacques Rougerie has his way, that will change soon.

Jacqucs has designed a ship that will allow researchers to spend a long period of time observing the sea life and conducting experiments. The huge 167ft ship, named 'Sea Orbiter', consists of two areas—one above the water where the scientists and crew will live, and a lower pressurized deck (甲板), where scientists will be able to spend as much time as they wish. Since it is powered by sea currents and wind, he expects it to drift (漂流) along the oceans slowly, taking about two years to circumvent the globe.

Jacques will make their life as comfortable as possible in the ship. Besides being equipped with the latest sailing tools and communication equipment, the ship will also have a gym, a television and a DVD player. And these guys will not be eating freeze-dried food like astronauts. Instead, Jacques, an accomplished chef, plans on cooking them delicious meals every day.

The biggest problem to this giant ship is the cost, which is expected to be over $500 million—per ship! However, Jacques, who strongly believes that the secrets of our oceans may be the key to solving global warming and a vital supply for food and medicine in the future, is confident he will be able to convince governments all over the world to help out, and expects to start construction on not one, but four or five of these amazing ships soon!

小题1:Why can’t ocean researchers explore the deep oceans for a long time?

A.Because they can’t stand the high water pressure.

B.Because it’s too cold in deep ocean.

C.Because time for experiments is too limited.

D.Because it’s dangerous to observe the sea life.小题2:The underlined word "circumvent" probably means         .

A.fly away

B.get around

C.travel through

D.move into小题3:From the fourth paragraph we can learn that       .

A.Jacques intends to design the ship mainly for sightseeing and traveling

B.living a comfortable life helps to do the ocean research quickly

C.it’s much more expensive to eat freeze-dried food

D.researchers on Jacque’s ship will live more comfortably than astronauts小题4:Which of the following would be the best title for the text?

A.Sea Orbiter—the ship of the future

B.A new way to explore the deep oceans

C.A great architect—Jacques Rougerie

D.Travel around the globe in Sea Orbiter

单项选择题