如图所示,固定的水平长直导线中通有电流I,矩形线框与导线在同一竖直平面内,且一边与导线平行.线框由静止释放,在下落过程中( )
A:穿过线框的磁通量保持不变
B:线框中感应电流方向保持不变
C:线框所受安培力的合力为零
D:线框的机械能不断减小
以下具有生物膜结构的细胞器是( )①线粒体②核糖体③中心体④高尔基体⑤内质网⑥液泡⑦溶酶体⑧叶绿体
there, time, happy, trip, busy
Ms. Brown is a teacher. Her students are ____ these days because of (因为) the school ____ to the Summer Palace. It's next week. But she is so ____ these days and she doesn't have ____ to go. She tells her students about it and they are not happy. But at last, the students persuade (说服) her and she decides (决定) to go ____ with her dear students.
如图是某太阳能热水器,向其中注入50kg的水,阳光照射一段时间后,水温从10℃升高到50℃.水的比热容是4.2×103J/(kg•℃).试求: