问题 选择题

如图18-1-12所示的电路中,L是电阻不计的电感线圈,C是电容器,闭合开关S,待电路达到稳定状态后再断开开关S,LC电路中将产生电磁振荡.如果规定电感L中的电流方向从a到b为正,断开开关时刻为t=0,那么在图18-1-13中哪个图能正确表示电感线圈中的电流i随时间t变化的规律(    )

图18-1-12

图18-1-13

答案

答案:A

电键断开的瞬间相当于放电完毕的瞬间,此时电流最大且与规定的正方向相同,故A正确.

阅读理解

阅读理解

     In Britain all children have to go to school between the ages of 5 and 16.  In the US children must go

to school from the age of 6 to the ages between 14 and 16, depending on the state they live in.  

     Subjects

     In England and Wales the subjects taught in schools are laid down by the NATIONAL

CURRICULUM, which was introduced in 1988 and sets out in detail the subjects that children should

study and the levels of achievement they should reach by the ages  of 7,11,14,and 16, when they are

tested.

     The National Curriculum does not apply in Scotland, where each school decides what subjects it  

will teach.

     In the US the subjects taught are decided hy national and local governments. 

     Whereas British schools usually have prayers and religious instructions, American schools are not

allowed to include prayers or to teach particular religious beliefs.

     Examinations

     At 16, students in England and Wales take GCSE examinations.  These examinations are taken by

students of all levels of ability in any of a range of subjects, and may involve a final examination, an

ASSESSMENT of work done during the two-year course, or both of these things.  At 18 some students

take A-LEVEL examinations, usually in not more than 3 subjects.  It is necessary to have A-Ievels in

order to go to a university of POLY-TECHNIC.

     In Scotland students take the SCE examinations.  A year later, they can take examinations called

HIGHERS, after. which they can either go straight to a uruversity or spend a further year at school and

take theCertificate of Sixth Year Studies.  In Scotland the  university system is different from that in

England and Wales.  Courses usually last four years rather than  three, and students study a large number

of subjects as  part of their degree.

 

1.  According to the passage, children have to go to school between the ages of        in both Britain and

     the US.

A. 5-14  

B. 6-14  

C. 5-15  

D. 6-17

2. In  which parts of the world are the subjects taught only decided by the nation?

A.  England and Wales. 

B.  England and Scotland. 

C.  US and Britain. 

D.  Wales and Scotland.

3.  As for the A-LEVEL examination, it involves      

A. final examination

B.  assessment of work

C.  not more than 3 subjects

D.  Both B and C

4.  Which of the following is TRUE?

A. In the US, only local government can decide the subjects. 

B.  In Scotland,  students can take either the SCE examinations or the Certificate of Sixth

      Year  Studies.

C. In England, Wales and Scotland, students need to study religion.

D.  As for a 16-year-old student in England and Wales, he has to take both GCSE examinations

     and final examination.

单项选择题