问题 计算题

一电阻为R的金属圆环,放在匀强磁场中,磁场与圆环所在平面垂直,如图(a),已知通过圆环的磁通量随时间t的变化关系如图(b),图中的最大磁通量和变化周期T都是已知量,求:

(1)在t=0到t= T/4的时间内,通过金属圆环横截面的电荷量q

(2)在t=0到t=2T的时间内,金属环所产生的电热Q

答案

  Q=16

题目分析:(1)此过程中,

在在t=0到t= T/4的时间内磁通量变化量为

(2)在t=到t=和在t=到t=T时间内,环中的感应电动势E2=0.

在t=0到t=时间内,环中的感应电动势E=.

由欧姆定律可知在以上时段内,环中的电流为I3.

在t=0到t=2T时间内金属环所产生的电热Q=2(IR+IR).

联立求解得Q=16.

点评:根据给定的图象得到感应电动势,再根据欧姆定律求出金属环中的电流从而进一步得到焦耳热;

单项选择题
阅读理解

A HOUSE WITH A HISTORY

Foulsham House is a fine,stone house of the 1790s.It stands by the River Byre,in twenty-five hectares(公顷)of the best farmland in the southwest.

Smithson built the house,and the story goes back to George,the young Prince of Wales,who fell in love with the beautiful lady Kitty Wake,at one of the first Lord Foulsham’s wild woods parties.In the past many great men rode on the hills about Foulsham House,and many fine ladies took tea in the Green Room.

The house has eight bedrooms,three bathrooms,two living-rooms and a dining room with a real Adam fire-place(壁炉).The gentleman’s library has a view over the park and the river.All rooms are light and airy(空气通畅的),with wood,high windows,and wood floors.

At the back of the house,where the third Lord Foulsham kept the horses,there is garage-space(停车的地方)for four cars.In many other ways,this house of the 1790s meets the needs of the 2000s.

  If you wish to know more about Foulsham House,write to:

Harvey,Platt,Longford & Sons,

6,Castle Green,Gilham,Byreside.

小题1:The writer writes this passage to ________.

A.persuade people to buy it

B.give some information about Foulsham House

C.tell a love story

D.describe the beauty of a best farmland小题2:People say that ________.

A.Smithson built the house for Lord Foulsham’s wild parties

B.Prince George fell in love with Kitty Wake at Foulsham House

C.Prince George and Kitty Wake fell in love with the Green Room

D.Lord Foulsham fell in love with a lady in Wales小题3:The library ________.

A.has a fine view of the park and the river

B.is where great men and fine ladies took tea

C.has an Adam fire-place,and a real wood floor

D.has eight bedrooms,three bathrooms and two living-rooms