英语周报2018-2022第17期答案

第一节One possible versionDear Fairy,Im pleased to hear that you want to learn something about Calligraphy Club in our school.The Calligraphy Club is divided into primary class and advanced class. Primary class is suitable for peopldewithout foundation while the teaching of advanced class is more specialized. There are two lessons a week foreach level. The classroom is on the third floor of Student Activity Center. The general requirements ofcalligraphy are very simple. In addition to mastering some basic skills, the most important thing is persistence.Each day the learners have to spare their free time to stick to practice.Finally, I suggest you can come to class to experience if you like. Then decide whether to join the club.ours truly,Li Hua

4.D【解析】本题考查远距离输电。在用电高峰时,并联的用电器增多,用户消耗的电功率增加,选项A错误;用户消耗的电功率增加,则电源的输出功率增大,所以升压变压器的输出功率增大,又升压变压器的输出电压U2不变,根据P=UI,可知输电线上的电流l增大,根据Us=l线r,输电线上的电压损失增大,则降压变压器的输入电压U3=U2U减小,降压变压器的输出电压减小,选项B错误输电线上损失的电功率△P=陵r增加,选项C错误;电能的输送效率为”数-U1×100%=2-U×100%,因为升压变压器的输出电U2不变,输电线上的电压损失U增大故效率η减小,选项D正确【关键点拨】解答本题的关键(1)在分析变压器问题时,一定要注意原副线圈中各量的决定关系:1决定U2,l2决定l,P2决定P1。(2)分析和计算输电线上的电压损失和功率损失时要用U=U注意PFR线

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