问题 选择题

如图所示,螺线管导线的两端与两平行金属板相连接,一个带正电的小球用绝缘丝线悬挂于两金属板间并处于静止状态.现将条形磁铁的N极突然插入螺线管,小球将发生偏转,若第一次插入的速度为v1,小球的最大偏角为θ1;第二次插入的速度为v2,小球的最大偏角为θ2,已知条形磁铁两次从同一位置插入相同的深度且v1>v2.则下列关于小球的偏转方向和偏转角大小关系说法正确的是(  )

A.偏向B板,θ1>θ2

B.偏向B板,θ1<θ2

C.偏向A板,θ1<θ2

D.偏向A板,θ1>θ2

答案

当磁铁插入时,导致线圈的磁通量发生变化,从而导致线圈中产生感应电动势,假设电路闭合,则由楞次定律可知,感应电流方向是从A极向下通过线圈再到B极,由于线圈相当于电源,因此B极电势高,所以带正电小球将向A板摆动;

当条形磁铁两次从同一位置插入相同的深度且v1>v2.则变化时间为t1<t2,根据法拉第电磁感应定律E=

△?
△t
可得,速度越大的,时间越短,则感应电动势越大,所以偏角越大,故D正确,ABC错误;

故选:D

阅读理解

第三部分阅读理解(满分40分)

第一节阅读选择(共10小题;每小题2分,满分20分)

A

A Father’s day is a day set aside for honouring fathers in church services and in

the home. It’s celebrated in the U.S. in the third Sunday of June. This idea was begun by Mrs John Bruces Dodd, who in 1909 persuaded an organization in Washington to

salute fathers with special church services. The idea was officially agreed to by President Woodrow Wilson in 1916. In 1924, President Calvin Coolidge suggested national celebration of the day to form closer relations between fathers and their children, and to impress upon fathers the full measure of their duties. The red or white rose is recognized as the official Father’s Day flower.

56. Father’s Day, at first, meant ______.

A. to honor fathers in church services and in the home

B. to win honor for fathers in church services

C. to do honour to fathers at home

D. to warn the fathers of their duties

57. Father’s Day was first celebrated by _____.

A. the French      B. the British      C. the German       D. the American

58. The first president who agreed to Father’s Day was _____.

A. Woodrow Wilson     B. Calvin Coolidge

C. George Washington   D. Abraham Lincoln

59. The president wanted Father’s Day to be a day on which _____.

A. people remembered their fathers

B. the relations between fathers and their children became closer

C. fathers must remember that they should be good fathers

D. both B and C

60. According to the passage, this idea was begun by______.

A. Woodrow Wilson      B. Calvin Coolidge

C. George Washington    D. Mrs. John Bruces Dodd

多项选择题