问题 问答题

如图所示,一个矩形线圈在匀强磁场中绕OO′轴匀速转动,磁场方向与转轴垂直.线圈匝数n=40,电阻r=1Ω,长l2=5cm,宽l2=4cm,角速度ω=100rad/s,磁场的磁感应强度B=0.2T.线圈两端外接电阻R=9Ω的用电器和一个交流电流表.求:

(1)线圈中产生的最大感应电动势;

(2)电流表的读数;

(3)用电器上消耗的电功率.

答案

(1)线圈中产生的感应电动势的最大值表达式为Em=NBSω=40×0.2×5×4×10-4×100=1.6V

    (2)电流的有效值I=

E
R+r
=
2
Em
2(R+r)
≈0.112A.

    (3)小灯泡消耗的电功率P=I2R=0.115W.

答:(1)线圈中产生的感应电动势的最大值是1.6V.

    (2)电流表的示数是0.112A.

    (3)小灯泡消耗的电功率是0.115W.

阅读理解

BEIJING, July 8 (Xinhuanet)--- A new hotel concept has been realized in a village in Northern Sweden, which aims to make the simple treehouse become a world-class destination for travellers. The Treehotel, located in a place called Harads, will consist of four rooms when it opens on July 17th: the Cabin, the Blue Cone, the Nest, and the Mirrorcube.

Two additional rooms are scheduled to open in October. The long term vision(想象) is even more expansive. “Our goal in five years is to have 24 rooms from 24 different architects,” says Treehotel co-founder Kent Lindvall.

The first six rooms were designed by five different architects. The Mirrorcube which stands four meters high and four meters wide, and the walls of which are made with a mirrored glass, has drawn widespread attention as it will be attached to a single tree. “It’s an interesting building. You can’t find anything else like this in the world today. It’s unique(独特的),” says Lindvall. “Everything will reflect in it---the trees, the birds, the clouds and the sun in the forest. So it could hardly be seen in the forest. This is untouched forest and we want to keep it the same way.”

Lindvall says the Treehotel’s vision proves a powerful draw, with enquiries(询问) coming in from far and wide. “I think what’s exciting here is that we’re just 60 km below the Arctic Circle. It means there’s a good possibility to have the northern lights in the winter and of course to have the midnight sun in the summer.”

The motto of the Treehotel is “Feel Free in a Tree” and expense will cost up to about $555.50 for two guests in the Cube, which is designed to hold up to four guests.

小题1:The underlined word “expansive” probably means _____.

A.costing a lot of money

B.covering a large area

C.requiring knowledge and skills

D.increasing suddenly and rapidly小题2:According to the passage, the Mirrorcube is a unique building because _____.

A.everything can reflect in it

B.it’s large with plenty of space

C.there is a large mirror wall in it

D.it has limited effect on local wildlife小题3:Which of the following statements is TRUE?

A.The Treehotel is ideally situated to enjoy the natural wonders.

B.The Treehotel is a great base to explore the many local places of interest.

C.Travellers can have a relaxed holiday at a reasonable price in the Treehotel.

D.The six rooms of the Treehotel was separately designed by 6 different architects.

填空题