《电工技术基础与技能》教材参考答案

《电工技术基础与技能》参考答案

第1章课程导入

1.1 认识电工实验实训室

思考与练习

1．直流交流

2．有电切断

1.2 安全用电常识

思考与练习

1．50mA 36V

2．正确安装用电设备安装漏电保护装置电气设备的保护接地电气设备的保护接零

3．用水和泡沫

复习与考工模拟

一、是非题

1．×2．√3．√4．×5．×6．√7．×8．√9．√10．×二、选择题

1．B 2．A 3．A 4．C 5．C

三、简答题

1．电工实验实训室通常的电源配置有：①两组可调直流稳压电压；②3～24V多挡低压交流输出；③单相交流电源；④TTL电源；⑤三相交流电压输出。

2．常用电工仪器仪表有：电流表、电压表、万用表、示波器、毫伏表、频率计、兆欧表、钳形电流表、信号发生器、单相调压器等。常用电工工具有：老虎钳、尖嘴钳、斜口钳、剥线钳、螺丝刀、镊子、电工刀、试电笔等。

3．实验实训室的安全操作规程：

（1）实验实训前必须做好准备工作，按规定的时间进入实验实训室，到达指定的工位，未经同意，不得私自调换。

（2）不得穿拖鞋进入实验实训室，不得携带食物进入实验实训室，不得让无关人员进入实验实训室，不得在室内喧哗、打闹、随意走动，不得乱摸乱动有关电气设备。

（3）任何电气设备内部未经验明无电时，一律视为有电，不准用手触及，任何接、拆线都必须切断电源后方可进行。

（4）实训前必须检查工具、测量仪表和防护用具是否完好，如发现不安全情况，应立即报告老师，以便及时采取措施；电器设备安装检修后，须经检验后方可使用。

（5）实践操作时，思想要高度集中，操作内容必须符合教学内容，不准做任何与实验实训无关的事，

（6）要爱护实验实训工具、仪器仪表、电气设备和公共财物。

（7）凡因违反操作规程或擅自动用其他仪器设备造成损坏者，由事故人作出书面检查，视情节轻重进行赔偿，并给予批评或处分。

（8）保持实验实训室整洁，每次实验实训后要清理工作场所，做好设备清

洁和日常维护工作。经老师同意后方可离开。

4．常见的触电类型：单相触电、两相触电和跨步电压触电。

第2章 电路的基础知识与基本测量

2.1 电路与电路图

思考与练习

1．电流 电源 负载 传输环节

2．通路 断路（或开路） 短路 电源短路

2.2 电流及其测量 思考与练习

1．正电荷 电子流动 2．24A

3．直流电流表 直流电流

2.3 电压及其测量

思考与练习

1．1.5V

2．直流电压表 直流电压

2.4 电阻及其测量

思考与练习

R ×100Ω 电阻调零 1

2.5 部分电路欧姆定律

思考与练习 1．正比 反比 R

U

I = 2．5Ω 3.6A

2.6 电能与电功率

思考与练习 1．1s

2．1210Ω 10W

复习与考工模拟

一、是非题

1．× 2．× 3．√ 4．× 5．√ 6．× 7．× 8．× 9．× 10．√ 二、选择题

1．B 2．C 3．B 4．A 5．D 6．B 7．C 8．D 三、问答与计算 1．23.3Ω

2．4.5A 0.25KW

3．59.52度 35.7元 四、实践与应用题 1．（1）一般新电池两端的电压大于1.5V ，而旧电池两端电压小于1.5V 。

（2）万用表测电池两端电压的操作步骤：①选择万用表的挡位与量程。把挡位与量程选择开关打在直流2.5V 挡。②万用表并接在电池两端。万用表的红表笔接电池的正极，黑表笔接电池的负极。③正确读数。

第3章 直流电路 3.1 闭合电路欧姆定律

思考与练习 1A 4V 0.5V

3.2 负载获得最大功率的条件

思考与练习

负载电阻R 等于电源的内阻r r

E P 42

m a x = 阻抗匹配 50% ??

3.3 电阻串联电路

思考与练习

15 0.2 1 0.4

3.4 电阻并联电路

思考与练习

1. 相等 通过各电阻的分电流之和 反比 反比 2．1：1 1：3 1：3

3.5 电阻混联电路 思考与练习 1. 5Ω 2. 4

3.6 基尔霍夫定律

思考与练习

1. 实际 参考 实际方向与参考方向相反

2．241I I I =+ 435I I I += 033244111=+---R I E R I E R I

复习与考工模拟

一、是非题

1．× 2．× 3．× 4．√ 5．√ 6．√ 7．√ 8．× 9．√ 10．√ 二、选择题

1．B 2．A 3．C 4．C 5． A 6．A 7．B 8．B 9．B 10．B 三、分析与计算 1．1.5A 2.85V 2．1.5Ω

3．串电阻 5Ω 4．66.7Ω 0.6A

5．（1）11=I A 6.02=I A 4.03=I A （2）8.51=U V 2.132==U U V 1=r U V

（3）8.51=P W 72.02=P W 48.03=P W 1=r P W 8=总P W 6．（1）321I I I =+

（2）0E -R I R I 13311=+ 0R I -E R I -22233=+ 7．S 打开时：Ω=6R AB S 闭合时：Ω=3R AB 8．

．

第4章 电容器 4.1 电容器的基本概念

思考与练习

1．能够储存电荷 电容器 2． 4103.24-? C

4.2 电容器的参数和种类

思考与练习 1．最大

2．4102? 0.02

4.3 电容器的连接

思考与练习

1．电荷量 电压

2．80V 40V 410.63-? C 410.27-? C

4.4 电容器的充电和放电

思考与练习

1．最大 逐渐减小 等于0 0 最大 电源

2．1K R 100R ?Ω?或 电容器内部可能断路 电容器内部已经短路

复习与考工模拟 一、是非题

1．× 2．× 3．× 4．√ 5．× 6．× 7．× 8．√ 9．× 10．√ 二、选择题

2.43A

1．C 2．B 3．C 4．C 5．B 6．A 7．B 8．C 9．D 10．B 三、分析与计算 1．3103-? C

2．共需4只电容器，两两串联后再两两并联。 3．（1）0.75μF 250V （2）电容器要被击穿

第5章 磁与电磁感应 5.1 磁的基本概念

思考与练习

1．电流的磁效应 2．右手螺旋定则

3．线圈中电流和方向如下图所示。

5.2 磁场的基本物理量

思考与练习

1．磁通密度 B 特斯拉 A B φ

=

2．磁感应强度 物质的磁导率 μ

B

H =

5.5 磁场对电流的作用

各载流导体的受力方向如下图所示。

5.6 电磁感应

运动导体中感应电流的方向如下图所示。

5.7 电感与电感器

思考与练习

1．电流变化 自感现象 自感电动势 2．铁心 磁心

复习与考工模拟

一、是非题

1．× 2．√ 3．× 4．√ 5．√ 6．√ 7．× 8．× 9．√ 10．× 二、选择题

1．B 2．B 3．C 4．A 5．C 6．C 7．C 8．D 9．D 10．C 三、分析与计算题

1．通电导体或螺线管周围存在的磁场 方向如下图所示。 2．310.61-?Wb 3．0.01T

第6章 磁与电磁感应 6.1 正弦交流电的基本概念

思考与练习

1．大小 方向 正弦规律 2．瞬时值 小字字母

6.2 正弦交流电的基本物理量与测量

思考与练习

1．10A 7.07A 314rad/s 50Hz 0.02S 60? 2．?15021u u 滞后

6.3 正弦交流电的表示法

思考与练习

1．解析式 波形图 矢量图 2．矢量图如下图所示。

复习与考工模拟

一、是非题

1．× 2．× 3．× 4．× 5．√ 6．× 7．√ 8．√ 9．√ 10．√ 二、选择题

1．D 2．C 3．C 4．B 5．C 6．D 7．C 8．D 9．B 10．A 三、分析与计算题

1．)45314sin(250?+=t u V 其波形图为如下图所示。

2．07.7=I A ?=300? 50=f Hz 当1.0=t S 时电流的瞬时值为

5A

2

3．)30314sin(21001?+=t u V t u 314sin 21502=V 它们的矢量图如下图所示。 5．（1）8.0=T mS 25.1=f KHz （2）6=-P P V V 3max =U V 1.2=U V

第7章 单相正弦交流电路 7.1 电感、电容对交流电的阻碍作用

思考与练习

1．31．85Ω 0.0159Ω 31.4Ω 12.56K Ω 2．耗能元件 储能元件

7.2 单一元件交流电路

思考与练习

1．0.1A )3010sin(21.0?+=t i π A 2．3.18A )150100sin(218.3?-=t i π A 3．0.31A )150100sin(231.0?+=t i π A

4．电压与电流的矢量图分别如下图所示。

7.3 RL 、RC 与RLC 串联电路

思考与练习

50Ω -36.9? 2A 160W 120Var 200V ?A 电容

7.4 电路的谐振

思考与练习

1．串联 电路的选择性变差 并联

2．最大 最大电压 电路的阻抗 中频选频

7.5 电能的测量与节能

思考与练习

1．标定电流值 最大电流值 2．直接接入 3．电子式

复习与考工模拟 一、是非题

1．× 2．√ 3．√ 4．√ 5．× 6．× 7．× 8．× 9．√ 10．√

11．√ 12．× 13．× 14．× 15．√

I

1

1．D 2．A 3．B 4．B 5．B 6．A 7．B 8．B 9．D 10．A 11．A 12．D 13．A 14．C 15．A 三、分析与计算题

1．（1）0.45A )60314sin(245.0?-=t i A （2）电压与电流的矢量图如下图所示。 （3）100W

2．（1）35A )60314sin(235?-=t i A （2）电压与电流的矢量图如下图所示。 （3）7707Var

3.（1）0.069A )90314sin(2069.0?+=t i A （2）电压与电流的矢量图如下图所示。

（3）15.2Var

4．（1）10Ω （2）22A （3）176=R U V 220=L U V 88=C U V

（4）3872=P W 2904=Q Var 4840=S V ?A （5）电路呈电感性

（6

8．提高功率因数的意义：①提高供电设备的能量利用率；②减小输电线路上的能量损失。

提高功率因数的方法：①提高用电设备自身的功率因数；②在感性负载上并联电容器。

第8章 三相正弦交流电路 8.1 三相正弦交流电源

思考与练习

1．)90sin(2220?-=t u V ωV )150sin(2220?+=t u W ωV 2．三相四线制 220V

8.4 用电保护

思考与练习

1．保护接地 保护接零 装设漏电保护器 2．中性点不接地的供电系统中

3．中性点直接接地的三相四线制供电系统中 保护装置

复习与考工模拟 一、是非题

1．√ 2．× 3．× 4．√ 5．√ 6．× 7．√ 8．√ 9．× 10．√

1．D 2．A 3．B 4．C 5．A 6．B 7．C 8．C 三、分析与计算题

1．)90314sin(2220?-=t u V V )150314sin(2220?+=t u W V 2．220=P U V 4.4=P I A 4.4=L I A

3．8.868=P W

4．变压器中性点不直接接地的供电系统中，如果不采取保护接地措施，那么人体触及带电外壳时，由于输电线与大地之间存在分布电容而构成回路，使人体有电流通过而发生触电事故。

5．在三相四线制供电系统中，中性线的作用：是使不对称负载两端电压保持对称，从而保证电路安全可靠地工作。 四、实践与应用题 1．星形联结 2．三角形联结

第9章 变压器 复习与考工模拟

一、是非题

1．× 2．× 3．× 4．× 5．√ 二、选择题

1．D 2．C 3．A 4．A 5． C 三、分析与计算题 1．80匝 2．240Ω 3．（1）200Ω （2）0.125W (3)0.018W 四、实践与应用题

1．二次绕组的直径更粗一些 2．为起到电磁屏蔽的作用

第10章 瞬态过程 复习与考工模拟

一、是非题

1．√ 2．√ 3．√ 4．√ 5．× 二、选择题

1．B 2．B 、C 3．C 4．B 5． C 三、分析与计算题

1．3)0(1=+i mA 0)0(2=+i 0)0(=+C u 2．6)0(=+C u V 1)0(=+C i mA 4)0(1=+R u V 3．（1）0.37 mA （2）0.69s

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Chapter 1 The Population I 2 populous 3 race 4 origin 5 geographical distPrelistening B 1 census ribution 6 made up of 7 comprises 8 relatively progressively 9 Metropolitan densely 10 decreased death rate 11 birth rate increasing 12 life expectancy D 1 a 18.5 mill b 80% c 1/2 d 13.4 mill e 2: 10 f 4% g 1990 h 40% i 3/4 j 33.1% 2 a 3 b 1 c 2 d 5 e 4 II First Listening ST1 population by race and origin ST2 geographical distribution ST3 age and sex III Postlistening A 1. People’s Republic of China, India 2. 281 mill

3. Hispanics(12.5%) 4. Texas 5. the South and the West 6. 20% 7. by more than 5 million 8. about 6 years 9. 2.2 years 10. a decreasing birth rate and an increasing life expectancy Chapter 2: Immigration: Past and Present PRELISTENING B. Vocabulary and Key Concepts immigrated natural disasters/ droughts/ famines persecution settlers/ colonists stages widespread unemployment scarcity expanding/ citizens failure decrease

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第二册Unit 9 Have you got what it takes? Mark No. Inside view Kate Conversation1So? Mark Mark the a careers fair on at Look, there's go? Schools. Do you want to Examination Well …I'm thinking of going into business Janet management. It's a possibility. What happens in a careers fair? Janet Really? different companies There are lots of Mark and they Mark Yes. advice, give you information about careers …that kind of thing. Kate Hey, let's go to the Careers Fair. It might give you some ideas. Janet…OK, I'll come. You coming, Kate? Janet Kate It was very interesting, wasnYeah, sure. But I've already decided on my 't it? You were having a long conversation with that man from career. the law firm. MarkKateWe know. You' a to be brilliant re going lawyer. Yes. They said there's a possibility of a job placement as an intern over the summer. Kate They'I–'Thats the plan 'm off to a law firm soon re going to let me know about it. as I get my degree. Janet Fantastic! Janet re so lucky. I wish I knew what I wanted You' to do. 1.Kate's plan is to go off to a law firm as soon as she gets her degree. Kate2.You have to plan ahead to be successful t you say something about teaching? Didn'3.It might give them ideas. Janet 4.Kate is having a long conversation with a m quite attracted 'm thinking about it. IYes, I'man from a law firm. 'to teaching. But Im not really sure yet. 5. The man said she could get a job placement Kate as intern over the summer. ve got lots of time. What about you, Well, you'Mark? What are your plans? Mark Conversation2m going to row for England. I' Kate Kate You know that job placement I told you about Seriously? –they've asked me to go for an interview. Mark be you want to if think I Problem No. is, Janet Thatahead plan to ve 'yousuccessful, got 's brilliant. When? – starting at the age of 12. Kate Two weeks' time …Janet …re not doing very well. 'So we Interviewer …

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Unit 1 Outside view Activity 1 Activity 2 one of the best universities most talented students well-known around the world have open doors good social life you want it to be on another campus it's a fun place go to concerts during the week Activity 3 library system online three / 3 four / 4 Brian leisure purposes the libraries listening in

Passage 1 1.2 2. 6 3.1 4.5 5.3 6.4 to Passage 1 again and rearrange the answers in the right column to match those questions in the left column. Ceahbgdf Passage 2 OC/O/C/O/C/C/O/C/O/OC to Passage 2 again and choose the best way to complete the sentences BDDBA Test CCBBD CDBCB C Unie 2 Outside view Activity 1 the video clip and match the speakers with the statements. K/K/T/S/T/K/S/K Activity 2

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22)2(121x a dm b dm dJ -+?= dx x a b dx b 23)2 (121-+=σσ 33121121ba a b dJ J σσ+==∴?)(12 22b a ab +=σ 3-3 如图3-28所示，一轻绳跨过两个质量为m 、半径为r 的均匀圆盘状定滑轮，绳的两端分别挂着质量为m 2和m 的重物，绳与滑轮间无相对滑动，滑轮轴光滑，求重物的加速度和各段绳中的张力。 解：受力分析如图 ma T mg 222=- （1） ma mg T =-1 （2） βJ r T T =-)(2 （3） βJ r T T =-)(1 （4） βr a =，2 2 1mr J = (5) 联立求出 g a 41= ， mg T 811=，mg T 451=，mg T 2 32= 3-4 如图3-29所示，一均匀细杆长为L ，质量为m ，平放在摩擦系数为μ的水平桌面上，设开始时杆以角速度0ω绕过细杆中心的竖直轴转动，试求：（1）作用于杆的摩擦力矩；（2）经过多长时间杆才会停止转动。 （1） 解：设杆的线l m = λ，在杆上取一小质元dx dm λ= gdx dmg df μλμ== gxdx dM μλ= 考虑对称 mgl gxdx M l μμλ?==20 4 1 2 （2） 根据转动定律d M J J dt ωβ== ? ?=-t w Jd Mdt 0 ω 图3-28 习题3-3图 图3-29 习题3-4图 T

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