问题 问答题

空间某区域存在水平方向的匀强磁场,磁感应强度B=1.0T.在磁场区域内有两根相距L=0.80m的平行金属导轨PQ、MN,固定在竖直平面内,如图所示.PM间连接有R=3.0Ω的电阻.导体棒cd沿导轨平面向右匀速运动,在回路中产生的电流I=0.60A.求:

(1)导体棒cd所受安培力F的大小;

(2)t=2.0s时间内电流在电阻R上产生的焦耳热.

答案

(1)导体棒cd所受安培力的大小F=BIL=1.0×0.6×0.8N=0.48N

(2)t=2.0s时间内电流在电阻R上产生的焦耳热Q=I2Rt=0.62×3.0×2.0J=2.16J

答:(1)导体棒cd所受安培力F的大小是0.48N;

    (2)t=2.0s时间内电流在电阻R上产生的焦耳热是2.16J.

阅读理解

Years ago, I lived in a building in a town. There was another building across form mine, and it was only a few meters away. There lived a woman whom I had never met. I could see her sit by the window each afternoon, drinking or reading.

Several months later, I noticed her window was very dirty. Everything was not clear through the window. I wondered why the woman didn’t wash her window.

One sunny morning, I decided to clean up my apartment, including washing my windows. Late in the afternoon when I finished the cleaning, I sat down for a rest by the window. What a surprise! The woman sitting by her window was clearly seen! Her window was clean! Suddenly, I realized I had made a mistake. I was watching her through my dirty window all the time!

That was quite an important lesson for me. Since then, whenever I wanted to judge(判断) someone, I asked myself first, “ Am I looking at him through the dirty window of my heart?” Then I try to clean the window of my own world so that I may see the world clearly.

小题1:The writer lived in           years ago.

A.a hotel

B.a village

C.a town

D.the countryside小题2:The woman often drank and read by the window           .

A.in the morning

B.in the afternoon

C.in the evening

D.the whole day小题3:One sunny morning, the writer decided to do some          .

A.reading

B.cleaning

C.shopping

D.cooking小题4:The writer was surprised to find the woman’s window was          .

A.far

B.broken

C.clean

D.dirty小题5:From the passage(文章), we can learn            .

A. we should judge ourselves before we judge others

B. we should judge others through the dirty windows

C. we shouldn’t clean the windows often

单项选择题