2021-2022 英语周报 七年级 新目标 9单项选择答案

16.B由于不知道金属杆中的电流方向,所以无法确定金属杆受到的安培力的方向,也就不能根据二力平衡确定金属杆受到的摩擦力的方向,故选项C和D均错误;当滑动变阻器的滑动触头由M点移动到N点时,滑动变阻器接入电路的电阻增大,由于电路的总电流不变,则流过金属杆的电流增大,金属杆受到的安培力增大,根据二力平衡可知,金属杆受到的静摩擦力増大,故选项B正确,选项A错误。

第一节短文改错It's been a long vacation, Last month, my aunt and uncle returned A work, so they neededsomeone to look after their child. I offered to give them the hand. I had thought i was able to dochildrenthat but things turned out so differentlydifferentFirst, they fought from time to time but I couldn t stop from it. Then, the mess they madereally annoys me. At lunchtime, I was busy preparing food while screaming to stop them beatingannoyedeach other. I wished I have not made that crazy offer. To her great relief, my grandma came thatadyafternoon, which meant that finally I was able to go home-after cleaning up the garbageeverywhere and collected the toys on the floor. How a busy daycollectingWhat

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