题干

如图所示,一半圆形铝框始终全部处在水平向外的非匀强磁场中,场中各点的磁感应强度随高度增加均匀减小,高度相同,磁感应强度相等。铝框平面与磁场垂直,直径ab水平,不计空气阻力,铝框由静止释放下落的过程中

A:铝框回路总感应电动势为零

B:回路中感应电流沿顺时针方向,直径ab两点间电势差为零

C:铝框下落的加速度大小一定小于重力加速度g

D:直径ab受安培力与半圆弧ab受安培力合力大小相等,方向相反

上一题 下一题 0.0难度 选择题 更新时间:2018-03-09 09:07:05

答案(点此获取答案解析)

C

同类题2

阅读理解

    Several days ago, Brenda had a car accident that led to one of her legs being cut off. Since then she didn't talk to anyone."I wish I could bring her friends to visit her," said Brenda's mother. "But it's a long bus trip." The nurse smiled, "Don't worry. We have a plan."Later that day, the nurse had taken Brenda to another room. "Here's your new roommate, Annie Wiggle-Do," the nurse introduced a dark-hair teenager on the other bed.

    As soon as the nurse left, she jumped out of her bed with her only foot and sat at the other end of Brenda's bed, "I lost my leg from bone cancer," she said. "What happened to yours?" Brenda was so shocked that she couldn't say a word. "You're lucky." Annie continued. "You've still got your knee. They had to take mine."

    "I'd like to have a chat with you, but my friends are coming any time now, so I have to get ready." Annie said when she took off her hair! Her head was completely bald(秃头的).

    "Oh, I forgot to tell you, the medicine they gave me to kill the cancer also killed my hair." Annie looked out her wigs(假发), brown and yellow, short and long, straight and curly."That's why I thought up 'Annie Wiggle-Do'." Annie smiled. "Get it? Any wig will do? Annie Wiggle-Do?" "When Annie's friends came, she introduced Brenda to them all. Before long, Brenda started chatting with Annie and her friends. They didn't make her feel like a strange person at all!

    The girls shared their names with each other. When it was time to go to bed, Brenda said, "Good night, Annie-Wiggle-Do. Can't wait till morning."