2022七下英语周报第34期答案

第四部分第二节Iwo davs before my birthday last vear. Dad came home earlv. As usual. Ihelped him carry his bags into his study: When I turned to leave. he said: "Hey. wouldyou like to help me clean my comb? It's been a while since I last cleaned"It hit methen why. as a child. helping my dad clean his comb was such a joy. That routinemeant that my dad was home early to spend the evening with Mum and I. It meantwould watch TV with us or play a few video games with me. It meant a happyloving familyI pass the clean comb back to Dad. I noticed the wrinkles next to his eyes.They are more noticeable when he smiles. but his smile is still as heartw arming asbefore. The smile of a father who just wants a good life for his family. Dad carefullyplaces his comb on top of his wallet. After so many years. he still organises hispersonal items in the same careful way. I guess some things never change. And forthat. I'm glad

23.(1)R2串联(每空2分)(2)电路图如图所示(3分)RR(3)0.22(0.20~0.24间均可)(3分)(3)0.22(0.20~0.24间均可)(3分)解析:本题考查电表的改装及描绘小灯泡的伏安特性曲线的实验(1)电压表的量程为2v,内阻为2ka2,故选用阻值为2k2的R2与电压表串联后可达到实验要求。(2)根据题述条件可知小电珠电阻约为109,因改装后的电压表的内阻4k远大于小电珠的内阻,故电流表应该外接;由于要描绘小电株的伏安特性曲线,滑动变阻器需用分压式接法3)设通过每个灯泡的电流为l根据闭合电路欧姆定律有E=U+4I(Rn+r),整理得1=4180,作出l-U的图线,图线与小电珠伏安特性曲线的交点对应的坐标为(185mA),.1V是小灯泡的电压,185mA是小灯泡的电流,由图可知,每个小灯泡消耗的电功率P=U=1.18×0.,185W=0.22w300150圃輯瞳辅圃離0

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