问题 问答题

如图所示,一小型发电机内有n=100匝矩形线圈,线圈面积S=0.10m2,线圈电阻可忽略不计.在外力作用下矩形线圈在B=0.10T匀强磁场中,以恒定的角速度ω=100π rad/s绕垂直于磁场方向的固定轴OO′匀速转动,发电机线圈两端与R=100Ω的电阻构成闭合回路.求:

(1)线圈转动时产生感应电动势的最大值;

(2)从线圈平面通过中性面时开始,线圈转过90°角的过程中通过电阻R横截面的电荷量;

(3)线圈匀速转动10s,电流通过电阻R产生的焦耳热.(计算结果保留二位有效数字)

答案

(1)当线圈与磁感线平行时,线圈中感应电动势的最大值,则为 Em=nBSω=3.1×102 V 

(2)设从线圈平面通过中性面时开始,线圈转过90°角所用时间为△t,

线圈中的平均感应电动势

.
E
=n
BS
△t

通过电阻R的平均电流

.
I
=
.
E
R
=
nBS
R△t

在△t时间内通过电阻横截面的电荷量Q=

.
I
△t=Q=
nSB
R
=1.0×10-2C,

(3)矩形线圈在匀强磁场中匀速转动产生正弦交变电流,电阻两端电压的有效值U=

2
2
Em

经过t=10s电流通过电阻产生的焦耳热Q=

U2
R
t

解得Q=4.9×103J.

填空题
阅读理解

阅读理解。

     下面五个人有些问题需要处理。阅读下面六个选项(A、B、C、D、E和F),选出符合各自需

求的最佳选项。选项中有一项是多余选项。

A. Pacha London www.pachalondon.com

     The world's most historic club is set in a building of the 1920s beautifully decorated in its original oak

paneling and features an impressive glass ceiling. You can enjoy beauty, style and elegance when clubbing

at London's most historic night club Pacha and appreciate works of some famous musicians.

B. Amika London www.amikalondon.com

     Amika plays host to the new super elite (精英) who are seeking the latest fashion trends. A unique

playground designed for fun. It is the final destination for major players and glitterati (上层人士) alike. It

features table reservations & bookings, events and corporate bookings.

C. SeOne Club London www.seonelondon.com

     SeOne is one of London's largest music clubs. Situated in the north of London, SeOne consists of five

rooms. It can be broken down into smaller spaces and can be used for parties as small as 100 people. SeOne

Club has attracted all kinds of promoters and event organizers, from corporate giants to dance promoters.

D. Koko Club www.koko.uk.com

     Situated at 1A Camden High Street, Central London, Koko Club represents a versatile (通用的),

21st-century club. It's very adaptable so it can be used for anything---from small comedy to international

music awards. A must visit!

E. Bar Rumba www.barrumba.co.uk

     Located in London's west end, Bar Rumba is one of London's leading late night clubs. Playing funk,

jazz, Afro-beat, Latin, Cuban, salsa, drum & bass, break beat. It has an amazing sound system for dance

music. Every night it delivers a different beat---from hip hop to Latin dance, from grime to jazz.

F. Club Colosseum www.clubcolosseum.com

     Situated in 1 Nine Elms Lane. Vauxall, London, Club Colosseum won the world's best club award in

1999. Now it features a new VIP room, a spectacular riverside bar with a view all over London & the

River Thames.

     1. Michael is a great painter and has just moved to London from America. On his arrival, Michael was

struck by the beautiful Thames. He dreams of going to a famous night club where he can easily appreciate

the unique view of the river.

      2. Nancy comes from Japan and wants to go to a world-famous night club with a long history to help

her know more about the British culture. Besides, Nancy likes to listen to great musical masterpieces.

     3. Laura is crazy about dancing and enjoys different dances with fascinating dance music. Now she is

in search of a night club that can offer her quality dance diversity.

     4. Lily would like to celebrate her eighteenth birthday at a proper night club next week. She intends to

invite over a hundred friends and relatives to her birthday party, most of whom are working in northern

London and are true music lovers.

     5. Harry is the general manager of a large company in London and he would like to go to a night club

which is fashionable. What's more, it should be suitable for someone of his status.