2022 英语周报 八年级 外研 27答案

第二节书面表达【写作指导】类型:通知审题时态:一般将来时和一般现在时为主人称:第三人称为主丰富校生活Para.1h陈述举办竞赛的目的增强学生食品安全意识国作思时间:竞賽时间和报名截止时间Pa2赛的时间地点和方式地点学校大礼堂报告厅芋方式:问答Para.3呼吁同学们积极参加【佳作展台】Noticecontest concerning the subject is to be held in our scho. a knowledgeAimed at raising students' awareness of food safetyThe contest is scheduled in the school hall from 2: 00 pm to 4: 00 pmon November 27th. It mainly consists of two rounds. First, all competitorsare required to answer five questions about food safety. The top 20competitors will have the opportunity to compete in the second roundwhere they will be asked another five more challenging questions. If youare interested, please sign up at the Student Union office before November20thLooking forward to your active participation【亮点梳理】亮点词汇: aimed at, awareness, schedule,berequired to do, sign up亮点结构:分词短语作状语( Aimed at raising studIents'awareness ofod safety), where引导的非限制性定语从句( where they will be askedanother five more challenging

12.(1)AC(2分)(2)1500(2分)(3)3000(2分)(4)大于(3分)解析:(1)用欧姆表测电阻时要进行欧姆调零,即将欧姆表两表笔短接,此时被测电阻为零,调节欧姆调零旋钮使指针指在表盘右侧零刻度线上,欧姆表刻度盘右边示数小,左边示数大,A项正确、B项错误;欧姆表的工作原理是应用闭合电路的欧姆定律,设欧姆表的内阻为R内,待测电阻为R,欧姆表内置电源的电动势为EE,由闭合电路的欧姆定律得1“R内+RI与R,不成正比,不是线性关系,故欧姆表的表盘刻度不均匀,R,变化量相等时,R越小I变化较大,R越大变化较小,因此欧姆表盘左边刻度比较密,右边刻度比较疏,C项正确、D项错误。(2)=E1.5V3×10-3A1500。(3)欧姆表的内阻R内3×103=15009,由闭合电路欧姆定律得×3×10-3A1500+R解得R=30009(4)R内=了,电源的电动势降低欧姆调零时欧姆表内阻R内变小,用欧姆表测电阻时,电流lER内+R.RR内十Rx1+R,由于R内变小,减小,指针往左偏故测量值大于真实值。

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