题目

将下列句子改为被动语态。【1】People plant bananas in some parts of southern China.【2】The students keep the classroom clean every day.【3】My friend sent me a beautiful card for my birthday.【4】I took these photos last Sunday.【5】Who sang this song?【6】We can’t see the stars in the day. 答案：【答案】【1】 Bananas are planted in some parts of southern China. 【2】 The classroom is kept clean by the students every day. 【3】 A beautiful card was sent to me for my birthday by my friend. 【4】 These photos were taken by me last Sunday. 【5】 Whom/ Who was this song sung by? 【6】 The stars can’t be seen in the day. 【解析】【1】由主动句改为被动句时，把如图甲所示，在一个正方形金属线圈区域内，存在着磁感应强度B随时间变化的匀强磁场，磁场的方向与线圈平面垂直．金属线圈所围的面积S=200cm2，匝数n=1000，线圈电阻r=1.0Ω．线圈与电阻R构成闭合回路，电阻的阻值R=4.0Ω．匀强磁场的磁感应强度随时间变化的情况如图乙所示，求：（1）在t=2.0s时刻，穿过线圈的磁通量和通过电阻R的感应电流的大小；（2）在t=5.0s时刻，电阻R消耗的电功率；（3）0--6.0s内整个闭合电路中产生的热量．