课时达标训练(七)
高二英语外研版选修七课时达标训练 Module 3 Period 2
2019年4月课时达标训练Ⅰ. 单词拼写1. Lu Xun is one of China’s most famous novelists(小说家).2. What are you two whispering(低语)about over there?3. That man’s brother seized(抓住)him and took him away.4. This platform would serve(充当) as a port and a railway station.5. I had no money left and was desperate(绝望的).6. The photo shows a famous scene(场景) from the film called Oliver Twist.7. The last Ming emperor hanged(吊死) himself from this tree.8. You should reward (奖励)them according to their contribution.9. She cares about the welfare(福利) of everyone.10. Food could be produced and there would be less or no starvation(饥饿).Ⅱ. 短语填空1. We stared at him in astonishment.2. No sooner had he left the house than his father came back.3. I am fed up with his constant complaints.4. Only a few people raised their hands in support of the proposal.5. He picked out a blue shirt that would go well with his pants.6. I am eager for news about them.【补偿训练】We are eager to know(know) the result after the exam.7. In flat open country there is plenty of grass for the cattle to feed on.8. As a reward for being good, the teacher bought all the students pizza.Ⅲ. 完成句子1. We saw many reporters on the scene(在现场) of the accident.2. These insects feed on(以……为食) a special kind of grass.3. He was rewarded for(因……受奖赏) his discovery in the field of medicine.4. They seem to be talking about something in a whisper(低声的).5. No sooner had we left the village(我们刚一离开村子) than it began to rain.6. Seize the chance(抓住机会)or you’ll regret.7. The beautiful girl serving as(担当, 担任) a hair dresser for a year is a manager now.8. We are eager to (渴望)make progress in the exam.9. It’s whispered that (人们私下说)he has made a fortune abroad.10. To my great astonishment(令我非常吃惊的是), she remembered my name after twenty years.【补偿训练】语法填空1. Her death should serve as a warning to other people.2. The policeman managed to seize (seize) the knife from the robber.3. He took a deep breath, desperately (desperate) trying to keep calm.4. When he was walking on the steel rope, everyone on the ground looked at him in astonishment(astonish).5. You should hold on to your dream no matter what happens in the future.6. I hammered a tack into the wall and hung (hang)a small picture from it.7. Hardly had he got home when he realized that he had left his keys in the office.8. He will sooner or later be rewarded (reward) for his kind conduct.。
高二英语外研版选修七课时达标训练 Module 1 Period 3
2019年4月课时达标训练Ⅰ. 写出下列句子中黑体单词的汉语意思1. CCTV will give the fans live broadcast of the World Cup. (现场直播的)2. The child is excited to see the real live fish. (活的)3. They live a comfortable life in the countryside. (过……生活)4. Zhang Ziyi is a world-famous film star who has starred in many famous films. (明星)(主演)5. The fish tastes delicious. (尝起来)6. The soup has little taste. (味道)7. The color and style is a matter of personal taste. (爱好)8. All plants need light and water. (植物)9. His home is near a chemical plant. (工厂)10. The field had been planted with corn. (种植)Ⅱ. 选择适当的词填空1. The brain needs a(n)continuous supply of blood.2. Though she is wealthy, the lady does not feel very happy.3. We sell good quality food at reasonable prices.4. The boy is good at grammar, but poor in pronunciation.5. I owe you a(n)apology for my rudeness yesterday.6. Facing the south, the room is comfortably warm.7. To her satisfaction, business has been good in the first two months.8. Young mothers should be taught how to raise their babies in a(n) scientific way.9. “Here we are! ” the boy shouted in a(n) cheerful voice.10. We heard the hostess’ announcement as soon as we got on the plane. Ⅲ. 用所给词的适当形式填空1. The story was so moving that nearly everybody was moved to tears. (move)2. We are interested in the novel which is very interesting. (interest)3. I am worried about the result. I have never spent a more worrying day. (worry)4. We were all tired out when we got to the top of the hill. We had never thought the climb was so tiring. (tire)5. His kind words were very encouraging. Though we had lost the match, we were encouraged and were determined to train harder. (encourage)6. At that moment I saw him crossing the road. (cross)7. I was glad to see the children well taken care of. (take)8. It’s wrong of you to leave the machine running. (run)9. I was surprised to find my hometown changed so much. (change)10. Do you know the boy lying under the big tree? (lie)Ⅰ. 语法填空阅读下面材料, 在空白处填入适当的内容(1个单词)或括号内单词的正确形式。
七年级生物下册 3.5.3 神经调节的基本方式课时达标练习(含解析)济南版(2021学年)
七年级生物下册3.5．３神经调节的基本方式课时达标练习（含解析)(新版)济南版编辑整理:尊敬的读者朋友们:这里是精品文档编辑中心，本文档内容是由我和我的同事精心编辑整理后发布的，发布之前我们对文中内容进行仔细校对，但是难免会有疏漏的地方,但是任然希望(七年级生物下册３．５.3 神经调节的基本方式课时达标练习（含解析）（新版)济南版）的内容能够给您的工作和学习带来便利。
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５。
3 神经调节的基本方式【双基巩固】1．做膝跳反射实验时,应迅速正确叩击受试同学的( )Ａ。
膝盖ﻩB。
膝盖下方的韧带ﻩC．小腿ﻩD。
大腿2。
神经调节的基本方式是（)A。
反射弧ﻩB.应激性ﻩﻩﻩＣ．适应性ﻩﻩD.反射3。
下列叙述中不属于反射的是( )Ａ。
手被火烧立即缩回ﻩﻩ B.斑马逃避狮的追捕C．下雨了,迅速寻找避雨的地方ﻩﻩD.含羞草受到触碰,叶子闭合4。
下图中①②③④⑤组成的神经结构称为( ）A。
神经元ﻩﻩﻩＢ。
神经中枢C。
反射弧ﻩD。
神经系统5．人体的反射弧中,下列哪个结构受损,在偶然被针刺到时既不会发生缩手反射也不会产生疼痛感( )A．传入神经纤维ﻩﻩﻩＢ.传出神经纤维C.效应器ﻩﻩD.大脑皮层痛觉中枢6。
下列反射活动中,属于条件反射的是( )A。
婴儿吮吸ﻩﻩﻩﻩﻩB.吃梅子唾液分泌增多C。
膝跳反射ﻩﻩﻩﻩD.学生听到上课铃声立即进入教室7.下列哪种反射仅仅由脊髓里的神经中枢控制完成( )Ａ.手不小心碰到火立即缩回ﻩＢ．下课铃一响就冲出教室Ｃ．看到酸梅分泌唾液ﻩﻩﻩﻩD。
听人说到酸梅分泌唾液８。
下列与成语“望梅止渴”条件反射类型相同的反射是（)Ａ.缩手反射B。
谈虎色变ﻩC。
老马识途Ｄ。
高二英语外研版选修七课时达标训练 Module 4 Period 2
2019年4月课时达标训练Ⅰ. 单词拼写1. Teachers should learn various techniques(技巧)for dealing with problem students.2. This seems, therefore, to be an approach(方法) worth exploring.3. What’s uncertain is precisely how it will emerge(出现).4. The same principle applies to our vocal (嗓音的)chords.5. He only lay without movement(运动).6. She started dancing to the rhythm(节奏)of the music.7. I think that the art of a storyteller is to take the story and improvise(即兴表演) on it.8. Union membership and union power are declining(下降).Ⅱ. 选词填空side by side, be bored with, rather than, consist of, experiment with, the moment, in decline, take advantage of1. The children are bored with eating the same kind of lunch every day.2. We had better take advantage of the warmer weather by going for a walk this afternoon.3. Even though they have been living side by side for 20 years, the neighbors are not very friendly.4. I would prefer to spend the weekend at home rather than drive all theway to the outside of the city.5. A table tennis match shall consist of the best of three games or the best of five games.6. If you will experiment with the material, you must take the consequences.7. There is a widely held belief that educational standards are in decline.8. They went wild with joy the moment they heard the news.Ⅲ. 单句改错1. In playing volleyball you have the advantage over being tall.(over→of) 2. The company is on decline because of falling demand.(on后加the) 3. We walked in the street shoulder by shoulder.(by→t o) 4. A new approach to teach the English language is being used here in our school.(teach→teaching) 5. They prefer to go with us rather than to stay here alone.(去掉第二个to)。
2019-2020年七年级英语下册 Unit 7 Abilities 课时训练 (新版)牛津版
2019-2020年七年级英语下册 Unit 7 Abilities 课时训练（新版）牛津版A.Helping Hands ClubDid you see these activities? Did you join the Helping Hands Club? Match the pictures below with the correct descriptions.A. Cleaning the street.B. Giving a seat to someone on the bus.C. Helping people to repair the electrical things.D. Helping the old man.E. Helping farmers do farm workF. Collecting things for project hope1. ______2. ______3. ______4. ______5. ______6. _____B. who do you admire?Do you admire a person who does the activities? Write down his/her name and what he/her do in daily life .Name:The relation with you: Personality:Activities:Reading comprehensionA Giving others a helpAfter reading the newspaper article , Daniel wrote an e-mail to his friend Jim to tell him the story about the brave girl , Wang Fang , but he missed some words . Help him to complete it .When you are in fire , what should you do ? Write a T if the hint is right ,or write F .Hints and Tips1. ( ) HAVE A FIRE ESCAPE PLAN2. ( ) USE ANY WINDOW OR GATE3. ( ) SEND THE ALARM4. ( ) WALK QUICKLY, DON'T PANIC(惊慌)5. ( ) OPN ALL THE DOORS6. ( ) USE THE LIFT7. ( ) STAY LOW AND GO8. ( ) OPEN WINDOW AND WAVE THE SHEET OUT OF THE WINDOW .9. ( ) GO BACK INTO FIRE FOR SOME THINGS10. ( ) DECIDE ON A MEETING PLACE FOR KNOWN IF EVERYONE HAS GOTTEN OUT SAFELYC Stories about abilitiesRead two stories about different kinds of abilities and complete the exercises . C1 CommunicationYou speak, write a letter, make a telephone call. Your words carry a message. Peoplecommunicate with words. Do you think you can communicate without words? A smile on your face shows you are happy or friendly. Tears in your eyes tell others that you are sad. When you raise your hand in class, the teacher knows you want to say somethingor ask questions. You shake your head, and people know you are saying "No". You nod and people know you are saying "Yes". Other things can also carry messages. For example, a sign at the bus stop helps you to know which bus to take. A sign on the wall of your school helps you to find the library. Signs on doors tell you where to go in or out. Have you ever noticed that there are a lot of signs around you and that you receive messages from them all the time?People can communicate in many other ways. An artist can use his drawings to tell about beautiful mountains, about the blue sea and many other things. Books are written to tell you about all the wonderful things in the world and also about people and their ideas. Books, magazines, TV and radios and films all help us to communicate with each other. They all help us to know what is going on in the world and what other people are thinking about.Notes: communicate 交流 sign 招牌,标志Choose the proper answers according to the article .1.( )Can we communicate with each other without words?A. Yes, some times we can.B. No, we can't.C. No. It's impossible.D. Yes, we always do so.2.( )When we see somebody smile, then, he must be feeling ____.A. angryB. joyfulC. surprisedD. sad3.( )We can learn news from ____.A. newspapersB. radioC. TVD. ABC4.( )A sign at the bus stop tells you ____.A. how many buses there areB. what kind of bus it is5. ( ) where the bus comes and goes D. how much money you'll pay for the ticket6.( )What do you think is the q uickest way to communicate with your friend in another city?A. Writing a letter.B. Making a telephone.C. Drawing a picture.D. Asking someone else to take a message.C2 Can Animal be Made to Work for UsCan animals be made to work for us? Some scientists think that one day animals may be taught to do a number of simple jobs. They say that in a film or on TV we may see elephants, or monkeys, dogs, bear, or other animals doing a lot of things. If you watch carefully, you may find that those animals are always given something to eat in return for doing them. The scientists say that many differentanimals may be taught to do a number of simple jobs if they know they will get something to eat in return.Of course, as we know, dogs can be used to guard a house, and elephant can be used to do some heavy jobs. And we can also teach animal to work in factories.Apes(猿猴), for example, have been used in America to help make cars and scientists believe that these large monkeys may one day get in crops and even drive trains.Write a T if the sentence is ture. Write an F if it is false.( ) 1 Elephant can be used to do some heavy jobs because they are very heavy. ( ) 2 Dogs can be used to guard a house for his host because they are brave enough to get the stranger(陌生人)and thieves away from the house.( ) 3 Many different animals may be taught to do some simple jobs if they are sent to school.( ) 4 Only a few animals can be train to work for us.( ) 5 Many scientists are working hard to make monkeys get in crops and drive trains.D ListeningVocabulary DrillsA. In each row, which word does not belong to ? Circle the word.1. helpful kind warm-hearted selfish2. careful generous rude polite3. happy unhappy cheerful pleasure4. quick hurry slow fast5. grateful thankful benedictory ungratefulB．1. 2. 3.4. 5. 6.7.8. 9.C. Please find the correct meaning of each words.1. friendly A. always helps the poor2. polite B. not afraid of something3. generous C. very easygoing4. kind D. like to help others , a warm-hearted nature.5. brave E. gives seats to the elderlyD. Please complete the words with the meanings.1. H the person who always help the people2. G feel thankful, expressing gratitude.3. C Attentive to danger, error, or harm; cautious:4. Q the person who can do anything fastGrammar ExerciseA Talking about ability with ‘can’/ ‘could’A1 Make some sentences use ‘can/ could’ according to the pictures.shooting (Amy) swimming (Linda) diving (Fang Fang ) weight lifting (Chu Chu)Example: Amy couldn’t shoot last year.Amy can shoot this year..A2 They are talking about some abilities on housework, please fill in the blanks.(1)Amy: (Can) you (cook) now?Betty: Yes, I (can) cook many dishes.A: Really? But I ( ).B: It doesn’t matter. Last year, I ( ),either.A: Could you teach me?B: Of course, I think you ( ) learn it quickly.A: Thank you. I ( )cook, but I ( ) do some washing.B: Well, but I think it’s less interesting than cooki ng . Amy BettyA: Maybe.⑵Mei Mei: My mother ( ) cook very delicious dishes.Ling Ling : Oh, my mother ( ), because she is very busy.M: But I think you ( ) help your mother , and that’s not hardfor you.L: Yes, I think so. But now, I ( ) at all.Mei Mei Ling LingA 3 Please use ‘could and can’ to compare your abilities when you were a little child and now . Write at least 5 sentences ._______________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ____A4 Chooses the right answer.1: When you talk about your abilities, you can use: ( )A: can B: could C: be D: A and B2: When you talk about the abilities before , you can use : ( )A: could B: couldn’t C: can D: can’t3: Which is right below?A: coulds B: canes C: could not D: couldes4: Which has the same meaning to ‘can’?A: be able to B: want C: be5:Can you help me do some shopping?A: sorry, I can’t. B: certainly, I couldn’t.C: I couldn’t. D: sorry, I can.B Talking about possibility with ‘can’ / ‘could’ and chances with ‘may’ / might.B1 Read the sentences ,then complete the sentences by using can and could with the verbs.1 Jane studies English everyday ,and she always talks to others in English .She will speak English .Soon she _______ (talk)to her foreign friends from England in English .2 John has poor eyesight, so he always wear a pair of glasses .If he does not wear the glasses ,he will not see anything clearly.Today , he forgets to bring his glasses ,so he ________ (see)anything on the blackboard clearly.3 Sally is good at singing , she will be a singer in Singing Club.There will be a Singing Match, she________(be) the winner in the match.4 It was a rainy day last Sunday ,and it was raining all the day .We ______(go) to anywhere, but we _______(stay)at home.5 Linda did not review very well some months ago ,and she always talked to others in the classes .Linda_______-(get) the good mark in that exam.B2 Choose the right answer1.He asked me for this book many times．Please tell him that he______have ittomorrow.A．must B．mayC．shall D．Both B and C2.- Will your brother stay home tonight?I’ m not quite sure. He _______ to the cinema tonight.A. must goB. can goC. may goD. may be going3.．You_____ return the book now．You can keep it till next week if youlike．A．can' t B．mustn' t C．needn’t D．may not4.I thought you______ like something to read, so I have brought yousome books．A．may B．might C．could D．must5.．_____ you succeed and _______ you be healthy．A．May… may B．Wish… wishC．Hope … hope D. Should… mayB3 Mr Wu wants to check his students if they understand how to use ‘can’, ‘could’, ‘may ’ and ‘might ’ . He ask Sandy to finish the sentences by choosing the correct word . Help her finish them.1. ----Could I borrow your bike?----Yes, of course you ________ (could, can).2. Last year I ________ (can’t, couldn’t) swim, but I ________ (can, could) swim now.3. He ________ (can’t, may not) be a good student because he is often late for school.4. ---- ________ (May, Might) I go out now?---- No, you mustn’t. You must stay at home.6.Whose ______ (may, might) it be? I think it might be Simon’s.B4 Choose the answer .1. Jim, you should listen to the teacher ________ in class.A: careful B: carefully C: care D: carelessly2. Everyone should ________ his best to do things well.A: do B: to do C: does D: doing3. His mother is ill and he goes to the hospital to ________ her every day.A: look at B: look after C: look up D: look out of4. We look forward to ________ from you soon.A: hear B: hears C: hearing D: be hear5. In our class many students are good at ________ basketball, but I’m not.A: playing B: play C: to play D: to playing6. Can you teach me how ________?A: dance B: dancing C: to dance D: dances7. Do you know what happened ________ Tom last night?A: with B: of C: at D: to8. Please don’t put ________ into the rubbish bin because it’s very dangerous.A: something hot B: hot something C: anything hot D: hot anything 9. I’m not feeling _________ this morning and my mother asks me to stay at home.A: well B: good C: nice D: badly10. My friend Bob is ill ________ now. I must go to the hospital to see him.A: in the hospital B: at the hospital C: in hospital D: at hospital 11. Thank you ________ us this evening and we’ll have a good time together.A: join B: for joining C: to join D: for join12. The fire is very dangerous. It is very important ________ with fire.A: to careful B: for careful C: to be careful D: be careful 13. Please ________ when the train l eaves. They’ll go to Beijing tomorrow morning.A: look for B: look at C: find D: find out14. ________ you tell me the way to people’s Hospital?A: Could B: Do C: May D: Might15. I’m not at home ________ May, but I’ll be back ________ 8th June.A: in, in B: on, on C: in, on D: on, inIntegrated skillsA Parents’ meeting at schoolA1 It is parents’meeting this afternoon . Your master teacher wants to make a report about the students . He wants to make some record cards . So he should know some information about yourself . Help him finish the card in English .You can draw your appearance on the card.Good at :Weak at :Sports :Hobby :PersonalityTarget :A2 Mr Wu is reading Sally’Sally is from Class _______ , Grade _______ . She is a ________ and ___________ girl . She always helps others . She does well in _________ , _________ and ________. She is so _______ and ________ that teachers like her . She can get better ________ in ________ and _______ if she words harder . Sally likes _________, so she takes part in the club . She may __________ the violin competition next week . After classshe often plays _________ and she thinks doing sports can keep _________ .B Things you can or cannot doYour teacher wants to know what you can do or cannot do . Put the sentences into English and complete them .1我能…._______________________________________________________________2我不能….._______________________________________________________________3没关系，我能把它唱好。
高二英语外研版选修七课时达标训练 Module 1 Period 4
2019年4月课时达标训练Ⅰ. 用所给词的适当形式填空1. Her books have been in popularity recently. (popular)2. It turned out to be a very interesting and lively debate. (live)3. Instantly the girl saw her mother, she burst out crying. (instant)4. Please confirm your telephone message by writing to me. (confirm)5. They have appointed Lang Ping head coach of the Chinese women’s volleyball team. (appointment)6. There is a puzzled expression on his face and I am puzzled to know what to do. (puzzle)7. Absorbed in watching the car pas sing by, he didn’t notice his friends coming. (absorb)8. The government is being asked to consider a plan to fix the date of the Spring Festival’s break. (consider)Ⅱ. 完成句子1. The film is based on a novel by Dickens.这部电影是以狄更斯的一本小说为基础的。
(base)2. He is used to living in the country now.他现在习惯了住在农村。
(used)【补偿训练】他过去曾是一名老师。
高二英语外研版选修七课时达标训练 Module 2 Period 2
2019年4月课时达标训练Ⅰ. 单词拼写1. He said that he would love her forever(永远), but after two years they got divorced.2. With the problem settled(解决), both sides were very pleased.【补偿训练】With so many things to settle(解决), the manager feels really puzzled.3. Children are easily influenced by their peers(同龄人).4. I had great difficulty finding the suitable(合适的) food on the menu in that restaurant.5. His strange behavior attracted(吸引) our attention.6. She agreed to rent (出租)the room to me.【补偿训练】Where is your rented(租来的) house?7. The food was delicious (可口的)and I ate too much.8. The problems facing the president are enormous (巨大的).9. You have to be highly competitive (好竞争的)to do well in sport these days.10. The highlights (最精彩的部分)of the match will be shown later this evening.Ⅱ. 单句改错1. I must settle down to finish writing the book. It is very urgent.()2. The house is not really suit for a large family. ()3. He was elected a chairman of the meeting. ()4. How fun it is to take part in that activity! ()5. That bank clerk ran away with an enormously sum of money. ()6. It is pity that you didn’t watch the play Tiger Mother Cat Dad. ()答案: 1. finish→finishing 2. suit→suitable 3. 去掉a4. How→What5. enormously→en ormous6. pity前加aⅢ. 完成句子1. I found myself standing alone on the deserted platform.我发现我形单影只地站在无人的月台上。
高二英语外研版选修七课时达标训练 Module 4 Period 3
2019年4月课时达标训练Ⅰ. 单句语法填空1. When he comes I’ll tell him about it.2. It was 3 months before the book was published.3. I’ll trust you to behave responsibly while I’m out.4. John thinks it won’t be long before he is ready for his new job.5. We did not start until the sun rose in the east.6. —Are you on holiday?—No, but I’d like to be (be).Ⅱ. 完成句子1. As time goes by, we have a better understanding of things around us. 随着时间的推移, 我们对自己周围的事物有了更好的理解。
【补偿训练】(同义句)With time going by, we have a better understanding of things around us.2. Mr Green has taught in that school since he came to China three years ago.自从格林先生3年前来到中国, 他就在那所学校教学。
3. By the time I got to school, the class had already begun.我到学校时, 已经开始上课了。
【补偿训练】到她回来时, 我们就把工作完成了。
By the time she comes back, we will have finished the job.4. When she comes, I shall tell her to wait for you.她来的时候我会告诉她等你。
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课时达标训练(七) 交变电流的特点
一、单项选择题
1．下列提到的交流电，哪一个不是指有效值( )
A．交流电压表读数 B．保险丝熔断电流
C．电容器击穿电压 D．220 V交流电压
2．(北京高考)一个小型电热器若接在输出电压为10 V的直流电源上，消耗电功率为P；
若把它接在某个正弦式交流电源上，其消耗的电功率为P2。如果电热器电阻不变，则此交流
电源输出电压的最大值为( )
A．5 V B．52 V
C．10 V D．102 V
3．(全国卷)一台电风扇的额定电压为交流220 V。在其正常工作过程中，用交流电流表
测得某一段时间内的工作电流I随时间t的变化如图所示。这段时间内电风扇的用电量为
( )
A．3.9×10－2 度 B．5.5×10－2 度
C．7.8×10－2 度 D．11.0×10－2 度
4．电阻R1、R2与交流电源按照图甲所示方式连接，R1＝10 Ω，R2＝20 Ω。合上开关S
后，通过电阻R2的正弦式交变电流i随时间t变化的情况如图乙所示。则( )
A．通过R1的电流有效值是1.2 A
B．R1两端的电压有效值是6 V
C．通过R2的电流最大值是1.2 2 A
D．R2两端的电压最大值是6 2 V
5．在阻值为R1和R2的两个电阻的两端，分别加上50 V的直流电压和某一交流电压，
则下面关于交流电压有效值的说法中正确的是( )
A．若两电阻在相等时间内产生的热量相等，则交流电压有效值为50/2 V
B．若R1＝R2，且两电阻热功率相等，则交流电压有效值为50 V
C．若R1＝R2，且两电阻产生的热量相等，则交流电压有效值为50 V
D．不论R1是否等于R2，只要两电阻的热功率相等，就有交流电压的有效值为50 V
二、多项选择题
6．下列关于交流电的说法中正确的是( )
A．交流电器设备上所标的电压和电流值是交流电的峰值
B．用交流电流表和电压表测定的读数值是交流电的瞬时值
C．给定的交流数值，在没有特别说明的情况下是指有效值
D．跟交变电流有相同的热效应的直流电的数值是交流电的有效值
7．某小型发电机产生的交变电动势为e＝50sin 100πt V。对此电动势，下列表述正确的
是( )
A．最大值是50 V B．频率是100 Hz
C．有效值是252 V D．周期是0.02 s
8．图甲、乙分别表示两种电压的波形，其中图甲所示电压按正弦规律变化。下列说法
正确的是( )
A．图甲表示交流电，图乙表示直流电
B．两种电压的有效值相等
C．图甲所示电压的有效值为220 V
D．一个周期内两种电流的电压平均值相等
三、非选择题
9．如图所示的电流i通过一个R＝1 Ω的电阻，它不是恒定电流。
(1)计算通电1 s内电阻R中产生的热量；
(2)计算该交流电的有效值。
10．先后用如图甲、乙所示的电流通过丙图中的电阻R，则电流表的示数分别为多少？
参考答案
1．解析：选C 根据对交流电有效值的定义及理解，C是交流电的峰值。
2．解析：选C 设该电热器的电阻为R，题中正弦交流电源输出电压的有效值为U，
则P2＝U2R；加直流电时，P＝10 V2R；又由最大值Um＝2U，可解出Um＝10 V，C正确。
3．解析：选B 根据电流的变化情况，分段计算求电功，W1＝I1Ut1＝3.96×104 J，W
2
＝I2Ut2＝5.28×104 J，W3＝I3Ut3＝1.056×105 J，则总功W＝W1＋W2＋W3＝1.98×105 J＝
5.5×10－2 度，B正确。
4．解析：选B 由题图可知通过电阻R2的电流最大值为0.6 2 A，故其有效值为0.6
A，根据串联电路的特点可得通过R1的电流有效值也为0.6 A，A、C错误；R1两端的电压
有效值为U1＝IR1＝6 V，B正确；R2两端的电压最大值为Um＝ImR2＝12 2 V，D错误。
5．解析：选B 对A、D项，因不确定两个电阻间的大小关系，所以不能确定交流电
的有效值，A、D错误；对B项，两只电阻相等，又有热功率相等，所以直流电压值就等于
交流电压的有效值，B正确；对C项，没有强调在相等的时间内产生相等的热量，C错误。
6．解析：选CD 对于交变电流，在没有特别说明的情况下是指有效值，交流电流表
和电压表的读数值是交流电的有效值，交流电器的铭牌上所标的电压和电流值也是有效值，
A、B错误，C、D正确。
7．解析：选ACD 最大值Em＝50 V，有效值为E＝Em2＝25 2 V，频率为50 Hz，周
期为T＝1f＝0.02 s，B错误，A、C、D正确。
8．解析：选CD 图甲、图乙均表示交流电，A错误；图甲是正弦式交流电，有效值
等于12×311 V≈220 V，C正确；图甲和图乙的有效值并不相同，B错误；两种电流一个周
期内的电压平均值都为零，D正确。
9．解析：(1)由图甲可知I1＝1 A，t1＝0.2 s，I2＝2 A，t2＝0.3 s，电流i在1 s内产生的
热量
Q＝2I21Rt1＋2I22Rt2＝2.8 J
(2)由I2Rt＝Q得电流I＝QRt≈1.67 A
即该交变电流的有效值为1.67 A。
答案：(1)2.8 J (2)1.67 A
10．解析：电流表的示数为通过R的电流的有效值。图甲中的i - t图象是正弦式曲线，
在前半个周期内，它的有效值与正弦式交变电流的有效值相同，I＝Im2＝52 2 A，后半个周
期不产生热量，则交流电在一个周期内通过电阻R所产生的热量Q交＝I2RT2
直流电在一个周期内通过电阻R所产生的热量
Q直＝I2ART
由于Q交＝Q直，所以I2RT2＝I2ART
解得IA＝I2＝2.5 A
图乙中周期为0.04 s，前0.02 s内i大小方向不变，产生的热量Q1＝I2mR·T2
后0.02 s内有效值为Im2，产生的热量
Q2＝Im22R·T2
由有效值的定义有
I2mR·T2＋Im22R·T2＝I2R·T
解得I＝2.5 3 A≈4.33 A
答案：2.5 A 4.33 A(或2.53 A)