问题 选择题

如图甲所示,在竖直方向上有四条间距相等的水平虚线L1、L2、L3、L4,在L1L2之间和L3L4之间存在匀强磁场,磁感应强度B大小均为1T,方向垂直于虚线所在平面。现有一矩形线圈abcd,宽度cd=L=0.5m,质量为0.1kg,电阻为2Ω,将其从图示位置由静止释放(cd边与L1重合),速度随时间的变化关系如图乙所示,t1时刻cd边与L2重合,t2时刻ab边与L3重合,t3时刻ab边与L4重合,已知t1~t2的时间间隔为0.6s,整个运动过程中线圈平面始终处于竖直方向,重力加速度g取10m/s2。则

A.在0~t1时间内,通过线圈的电荷量为0.25C

B.线圈匀速运动的速度大小为2m/s

C.线圈的长度为1m

D.0~t3时间内,线圈产生的热量为4.2J

答案

答案:A

题目分析:这段时间内线圈做匀速直线运动,设速度为v.根据平衡条件有:

联立两式解得:.故B错误.的时间间隔内线圈一直做匀加速直线运动,知ab边刚进磁场,cd边也刚进磁场.设磁场的宽度为d,线圈下降的位移为3d,则有:

,代入解得:d=1m,所以线圈的长度为:.故C错误.

在0~时间内,cd边从运动到,通过线圈的电荷量为:.故A正确.0~时间内,根据能量守恒得:

.故D错误.

单项选择题
阅读理解

One of the greatest contributions to the first Oxford English Dictionary was also one of its most unusual. In 1879, Oxford University in England asked Prof. James Murray to serve as editor for what was to be the most ambitious dictionary in the history of the English language. It would include every English word possible and would give not only the definition but also the history of the word and quotations (引文)showing how it was used.

This was a huge task. So Murrary had to find volunteers from Britain, the United States, and the British colonies to search every newspaper, magazine, and book ever written in English. Hundreds of volunteers responded, including William Chester Minor. Dr. Minor was an American Surgeon who had served in the Civil War and was now living in England. He gave his address as “Broadmoor, Crowthorne, Berkshire,” 50 miles from Oxford.

Minor joined the army of volunteers sending words and quotations to Murray. Over the next years, he became one of the staff’s most valued contributors.

But he was also a mystery. In spite of many invitations, he would always decline to visit Oxford. So in 1897, Murray finally decided to travel to Crowthorne himself. When he arrived, he found Minor locked in a book-lined cell at the Broadmoor Asylum for the Criminally insane.

Murray and Minor became friends, sharing their love of words. Minor continued contributing to the dictionary, sending in more than 10,000 submissions in 20 years. Murray continued to visit Minor regularly, sometimes taking walks with him around the asylum grounds.

In 1910, Minor left Broadmoor for an asylum in his native America. Murray was at the port to wave goodbye to his remarkable friend.

Minor died in 1920, seven years before the first edition of the Oxford English Dictionary was completed. The 12 volumes defined 414,825 words, and thousands of them were contributions from a very scholarly and devoted asylum patient.

小题1:According to the text, the first Oxford English Dictionary _________.

A.came out before minor died

B.was edited by an American volunteer

C.included the English words invented by Murray

D.was intended to be the most ambitious English dictionary小题2:How did Dr. Minor contributed to the dictionary?

A.He helped Murray to find hundreds of volunteers.

B.He sent newspapers, magazines and books to Murray.

C.He provided a great number of words and quotations

D.he went to England to work with Murray.小题3:Why did Dr. Minor refuse to visit Oxford?

A.He was shut in an asylum

B.He lived far from Oxford

C.He was busy writing a book

D.He disliked traveling小题4:Prof. Murray and Dr. Minor became friends mainly because __________.

A.they both served in the Civil War.

B.They had a common interest in words

C.Minor recovered with the help of Murray

D.Murray went to America regularly to visit Minor小题5:Which of the following best describe Dr. Minor?

A.Brave and determined

B.Cautious and friendly

C.Considerate and optimistic

D.Unusual and scholarly小题6:What does the text mainly talk about?

A.The history of the English language.

B.The friendship between Murray and Minor

C.Minor and the first Oxford English Dictionary

D.Broadmoor Asylum and is patients