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CMA7电动操作机构使用说明书

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4.2.2 控制回路控制回路经端子X1的／6、7端子，接至L1和N，中间接入
Q1的辅助触点和S8、S18，所以Q1、S8或S18动作，控制电压即中断。电机保护开关Q1的跳闸回路与控制回路连锁。
电机保护开关Q1带有分励脱扣线圈，可由按钮S5、安全电路或连动保护电路激励，安全电路是由凸轮开关S12、S13 和S14以及电机接触器K1、K2的辅助触点组成的，连动保护用时间继电器K21的常开触点。
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一、概述
CMA7型电动操作机构是有载分接开关分接变换操作的驱动和控制机构。 CMA7电动机构箱内装有驱动有载分接开关工作所需要的全部电气和机械装置，控制是按照逐级控制原理，即分接开关从一个工作位置变换到相邻的一个工作位置时，电动机构的动作是单一控制信号启动的，完成一次操作后自动停止。整个电动机构安装在变压器油箱的箱壁上，借助水平传动轴、中间伞齿轮盒及垂直传动轴与分接开关联结。 1.1 使用范围 CMA7电动操作机构用于驱动CM、CV型有载分接开关，以及无励磁分接开关。 1.2 使用条件：CMA7电动机构的使用环境必须满足下列条件 1.2.1 海拔高度不超过2000m，如超过须特殊注明。 1.2.2 环境温度不高于+55℃，不低于-25℃。温度低于-25℃时，请在订货时注明，我们可特殊设计； 1.2.3 与地平面的垂直度偏差不超过5%； 1.2.4 安装场所无严重尘埃及其它爆炸性和腐蚀性气体。

EPLAN例图4（精品）

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2019-2020届初三串联电路中欧姆定律的应用专项练习(含答案解析)

串联电路中欧姆定律的应用专项练习一、计算题1、滑动变阻器一般只在实验室中使用，图24甲是家用电器中常用的一种电位器，通过机械式旋钮调节阻值的大小。

小亮利用这种电位器自制了一个可调亮度的手电筒，其电路图如图24乙所示。

电源两端电压U为6 V且保持不变，小灯泡电阻R1为10Ω（不考虑温度对灯丝电阻的影响）。

开关S闭合后，求：（1）当电位器R接入电路的电阻R2为20Ω时，通过小灯泡R1的电流I ；（2）当电位器R接入电路的电阻R3为10Ω时，小灯泡R1的电压U1。

2、如图所示，电源两端电压U保持不变，电阻R1的阻值为6Ω，电阻R2的阻值为18Ω．当开关S闭合时，电压表示数为 3V．求：（1）电流表的示数 I；（2）电源两端的电压 U．3、为了防止酒驾事故的出现，酒精测试仪已被广泛应用。

交警使用的某型号酒精测试仪的工作原理如图25所示。

电源电压恒为8V，传感器电阻R2的电阻值随酒精气体浓度的增大而减小，当酒精气体的浓度为0时，R2的电阻为60Ω。

使用前要通过调零旋扭（即滑动变阻器R1的滑片）对酒精测试仪进行调零，此时电压表的为6V。

（1）电压表的示数为6V时，电流表的示数为多少？（2）电压表的示数为6V时，滑动变阻器R1的电阻值为多少？（3）调零后，R1的电阻保持不变。

某驾驶员对着酒精测试仪吹气10s，若电流表的示数达到0.2A，表明驾驶员酒驾，此时电压表的示数为多少？4、如何用一个电压表和一个已知电阻来测某未知电阻的阻值？小林设计了如图所示的电路．实验时，已知R1为9Ω，在闭合S的情况下，断开S1时电压表的示数为1.8V，闭合S1时，电压表的示数为2.7V．整个实验过程中电池的电压不变，求：（1）电源电压；（2）被测电阻R2的阻值．5、为了防止酒驾事故的出现，酒精测试仪已被广泛应用．交警使用的某型号酒精测试仪的工作原理如图所示．电源电压恒为8V，传感器电阻R2的电阻值随酒精气体浓度的增大而减小，当酒精气体的浓度为0时，R2的电阻为60Ω．使用前要通过调零旋扭（即滑动变阻器R1的滑片）对酒精测试仪进行调零，此时电压表的示数为6V。

2020中考物理压轴专题：动态电路分析(含答案)

2020中考物理压轴专题：动态电路分析（含答案）一、串联电路1.如图1所示,电源电压不变,闭合开关S,当滑动变阻器的滑片P向左移动时,请回答下列问题:(1)去表看电路,复杂电路可分别画出等效电路图,电路中的电流有条路径,电阻R、R1的连接方式是。

图1(2)判断电表的测量对象:串联不用分析电流表,各处电流都相等,重点分析电压表,电压表测量两端的电压(并联法)。

(3)判断滑动变阻器滑片P移动时相关物理量的变化情况:电源电压不变,滑片P向左移动时→R接入电路的阻值→电路中的总阻值→电流表的示数→电阻R1两端的电压→电压表V的示数。

电压表的示数与电流表的示数的比值(实质是滑动变阻器连入电路中的阻值);电压表示数的变化量与电流表示数的变化量的比值(实质是定值电阻R1的阻值)。

(均选填“变大”“变小”或“不变”)【规律总结】滑片移动引起的串联电路动态分析:首先确定电阻的变化,根据电源电压不变,确定串联电路电流的变化,再根据串联电路电阻分压(电阻大分得的电压就大),确定定值电阻及滑动变阻器两端电压的变化,根据电功、电功率的公式确定电功、电功率的变化,如图2所示。

(先电流后电压、先整体后部分)滑片的移动方向R滑的变化电路中电流I的变化定值电阻两端电压U定的变化滑动变阻器两端电压U滑的变化图22.如图3所示电路中,电源电压保持不变,闭合开关S,当滑动变阻器的滑片P从a端向b端滑动时,电流表A示数,电压表V1示数,电压表V2示数,电压表V1示数与电流表A示数的比值,电压表V2示数与电流表A示数的比值,电路消耗的总功率。

(均选填“变大”“变小”或“不变”)二、并联电路3.如图4所示,电源电压不变,闭合开关S,当滑动变阻器的滑片P向左移动时,请回答下列问题:(灯丝电阻不随温度变化)图4(1)去表看电路,复杂电路可分别画出等效电路图,电路中的电流有条路径,电阻R、灯泡L的连接方式是。

(2)判断电表的测量对象:并联电路不分析电压表,各支路电压相等且等于电源电压。

部编人教版九年级物理上册《第16章-电压电阻【全章】》精品PPT优质课件

移点法
例2 在如图甲所示的电路中，当闭合开关S后，两个电压表指针偏转均如图乙所示，则电阻R1和R2两端的电压分别为（ A ）
A.5.6V B.7V C.1.4V D.1.4V
1.4V 1.4V 7V 5.6V
解析：电压表 V1测的是电源电压， 0~15V； 7V 电压表 V2测的是电阻 R2 两端的电压，0 ~3V；1.4V 在串联电路中 U＝ U1＋ U2，则 U1 ＝ U － U2 ＝7V －1.4V ＝5.6V. 故本题应选 A.
例1 下列说法正确的是（ C ）
电路中有电压，但是不构成通路，就不会有电流。
A.电路中只要有电压，就会有电流 ×
B.电压一定会使物体中的电子不断移动 ×
C.电路中有电流，电路两端一定有电压√
电路中有电压，但是不构成通路，就
D.电流使导体中不断形成电压 ×
不会使电子运动。
电压是形成电流的原因，而电流不是形成电压的原因。
结论串联电路总电压等于各部分两端电压之和。
L1
L2
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U
U=U1+U2
例1 （多选）如图甲所示，电源电压是 8V且保持不变，开关 S闭合后，电压表的示数是 2V，则（ CD ） A.L1 两端的电压是2V B.L2两端的电压是6V C.L1两端的电压是6V D.L2两端的电压是2V
当S闭合时，等效电路图如图乙所示，电压表测的是L2两端的电压.
想想做做把几节电池串联起来组成电池组，用电压表分别测
量每节电池两端的电压，然后测量这个电池组两端的电压。它们之间有什么关系？
电池串并联的电压规律：
点击图片观看视频
结论： 1.串联电池组的总电压等于各个电池电压之和。 2.并联电池组的总电压等于一个电池的电压。

大金空调显示u1是什么意思故障怎样解决排除

大金空调U1是什么意思怎样解决排除大金空调故障代码U1故障内容：缺相、反相大金空调故障代码U1故障原因：电源反相；电源T相缺相；室外机P板故障。

大金空调故障代码U1细分六种故障：1、U1-01：电源反相/ 缺相(主机)2、U1-04：[电源接通的情况下]电源反相(主机)3、U1-05：电源反相/ 缺相(副机1)4、U1-06：[电源接通的情况下]电源反相(副机1)5、U1-07：电源反相/ 缺相(副机2)6、U1-08：[电源接通的情况下]电源反相(副机2)针对以上六种情况，大金空调售后维修工程师解决方法：1、检查外籍电源端子是否缺相。

2、更换1处电源线的相位，如故障依旧，更换控制P板一、大金故障代码(内机)没带压力表时检测低压压力〔ＰＨ〕2 Ｒ２２高压＝〔A0-----保护装置动作低压＝〔A1-----室内机P板不良Ｒ４１０Ａ高压A2-----风扇连锁器动作低压A3-----排水水位异常. A4-----热交换(1)温度异常A5-----热交换(2)温度异常五、检查热敏电阻A6-----风扇电动机过负荷过电流过或堵转. A7-----风向调整电动机堵转A8----AC输入过电流温度: －２０度电A9-----电子膨胀阀异常－１５度电阻为１AA-----加热器过热AH-----错误或着赃污－１０度为１１６AC-----空负载运作AJ----容量设定不良５度５１.９千欧姆AE----给水不足１０度４０千欧姆AF-----加湿器错误C0-----传感器异常１５度３１.８千欧C1---空白２０度２５千欧姆C2----空白２５度２０千欧姆C3----排水水位传感器异常３０度１６千欧姆C4-----热交换(1)温度异常C5-----热交换(2)温度异常３５度１３千欧姆C6----风扇电动机过负荷过电流连锁检测用传感器异常４０度１０.６千欧C7--风向调整电动机堵转检测用传感器异常４５度８.７千欧姆C8----AC输入电流传感器异常C9----吸入空气温度传感器异常CA---吹出空气温度传感器异常六、内机风扇马达CH----空白CC----湿度传感器异常 1 检查插接件的连CJ----温度传感器异常2检查马达电源电CE----辐射传感器异常CF----高压压力开关不良3检查马达控制电3 4检查旋转指令电二、大金室外机故障代码5检查旋转脉冲输4 1－－－E0----保护装置动作2－－－E1----室外机P板不良3－－－E2----空白E3----高压压力4－－－E4---低压压力5－－－E5----压缩机电动机过负荷E6----压缩机电动机过电流堵转6－－－E7-----风扇电动机过电流过负荷堵转7－－－E8-----AC输入过电流E9----电子膨胀阀错误EA----空白八、制冷能力EH----泵过电流堵转EC----水温异常Ｒ２２型低压４千EJ----现场追加保护装置动作EE----排水水位异常Ｒ４１０Ａ低压６千克－－２１千克EF----畜热单元异常H0----传感器异常Ｒ４１０Ａ高压２H1----空气温度传感器异常低压低于０.０７千H2----电源传感器异常高压高于３６千克H3----高压压力开关不良H4----低压压力开关不良压缩机温度高于６H5----压缩机电动机过负荷传感器家用ＶＲＶ制暖时动作，变频／定频H6----压缩机电动机过电流堵转检测用传感器异常H7----风扇电动机过电流过负荷堵转检测用传感器异常九、电子膨胀阀的H8----AC输入过电流传感器异常H9----室外温度传感器异常HA----吹出空气温度传感器异常１－３－６是否导HH----泵过电流连锁检测用传感器异常HC----水温传感器异常２－４－５是否导HJ----空白１－６２－６５０欧姆HE----排水水位传感器异常十、压力传感器的红———＋５ＶＤ黑———ＧＮＤ〔F2----NO.2系统保护装置动作F3----排出管温度异常绿———低压〔２F4----空白F5----空白黑———高压〔１F6----热交(1)温度异常十一、新冷煤表F7----空白F8----空白F9----空白FA----吐出压力异常大金内机型尺寸,4为9.5/6.4><50FH----油温异常50-60机型铜型,740X500>,<内FC----吸入压力异常内机63/71型11 </PIXTEL_MMI_FJ----空白FE---油压异常FF----油面异常十二、大金VRVJ0----制冷温度传感器异常A1 室内机印刷电动电机锁定C4热温度感应器系统异常。

工程光学习题1

(n 1)
习题1-8 如图1-6所示，光线芯的折射率为n1，包层的折射率为n2，光纤所在介质的折射率为n0，求光纤的数值孔径。
n2 sin I m n1 n0 sin I1 n1 cos I m n n
2 1 2 2
习题1-9 有一直角棱镜如图1-16所示，其折射率为n。问光线以多大的孔径角入射时，正好能够经其斜面全反射后出射。如果棱镜用冕牌玻璃K9制造，计算该孔径角的值。
• 2.已知真空中的光速，求光在水（n=1.333 ）、冕牌玻璃（n=1.51）、火石玻璃（ n=1.65）、加拿大树胶（n=1.526）、金刚石（n=2.417）等介质中的光速。 c 3 10 c v n • 答：根据 v ，分别代入数字得： n n m / s 3 10 v • （1）在水中（注意单位） 1.333 2.2510 m / s • （2）在冕牌玻璃中 • （3）在火石玻璃中 • （4）在加拿大树胶中 • （5）在金刚石中
L d lF
300m m d L lF f 3 lF
h1 f tanu h1 2 h2 tanu h2 2 lF h1 tanu1 f1 h h d tanu 1 1 2
1 1 2 l l r (1) 0, l l l , l 50m m

无限远轴上物点的共轭像点正好位于 r / 2处； (2) 0.1, l 550mm, l 55m m； (3) 0.2, l 300mm, l 60m m；
(1) l 时， 0； (2) l 1000mm时， 0.429 ； (3) l 100mm时， 1.5； (4) l 0时，l 0，物和像都位于折射球面的顶点， 0； (5) l 100mm时， 0.75； (6) l 150mm时， 0.667 ； (7) l 200mm时， 0.6；

串并联电路电压规律

10．李明同学在一次用有3V和15V两个量程的电压表测电压时，电压表的“-”接线柱已接入电路，在用15V量程试触时，指针位置如图所示，则下一步的实验操作应该是( D )
A．直接接入15接线柱，然后读数 B．直接接入3接线柱，然后读数 C．断开开关，接入15接线柱，然后闭合开关后读数 D．断开开关，接入3接线柱，然后闭合开关后读数
例、如图所示电路中，L1、L2、L3是三盏相同的灯
泡，V1的示数为6V，V2的示数为6V，问：
（1）L1、L2、L3的连接方式是什么？
（2）电压表V1、V2分别测的是谁的电压？
（3）电源电压是多少？
答：（1）L1、L2、L3
S
的连接方式是串联。
（2）电压表V1测的是
V
L1和L2两端的电压，V2 L
5．小明用电压表测电压时，电压表接线柱的接法如图 16-1-1所示。下列同组同学对此接法的看法中正确的是( D ) A．该电压表的测量范围是3～15V B．该电压表可以测出电压值 C．该电压表没有正接线柱 D．小明不能测出电压值
8．使用电压表时，必须把它
(选填“串联”或
“并联”)接在要测量的那部分电路的两端，使用时必
使
5、读数时要认清量程和分度值。
用
一、探究串联电路电压的规律
①测灯L1两端的电压 ②测灯L2两端的电压
L1
L2
L1
L2
③串联电路两端电压
④电源两端电压
L1
L2
L1
L2
⑤ 改变两个小灯泡的规格重做上述实验。
串联电路总电压等于各部分两端电压之和。
L1
L2
U1
U2
U
U=U1+U2
并联电路中，各支路两端的电压与电源两端电压的关系是怎样的？

西尼电梯图纸

CB-09 SQU SQD
0V + 24V OUT 0V OUT
下光电
200
202
下迫慢1
电锁
34 SWF KAS 33
14 KAD 13
44 KMC 43
44 KMY 43
L +5V COM
N
COM C9--04
SRK
SSU1
SSD1
SLU
SLD
SSU
SSD
+ 24V
TPB
+24V
T1 KMB L1
D
L2
L21
S 1
L2
KMC
T2
L2 KMY L3
T2
V1
M
L31 L3
T1
KMC L3 T3
T3
W1
N
PE J7-7 21 21 CM P0 CM PB PA
+12V 0V B A
KAD
C
KMY
22 22 EN FWD REV X1 X2 X3 Y1 COM CMY 30B 30C PA0 PB0 P0 CM J8-5 J8-6 J8-1 J8-2
* if power of eq or le 15kw omit device BKU
SCB
RB
B
10 (M2) 19 (MB) 20 (MC) 13(A1)
B1
B2
J7-9 KMB J7-10
21(31) 22(32)
BKU
3
0 RB
17(AC)
PE
A
0
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Design Standard
郦蒙良
Collate Technics

牛津版八年级英语暑假班—L1 The Zipper—名词—阅读A篇—词汇U1

Lesson 1 The zipperLet’s ReadThe zipper is a wonderful invention. How did people ever live without zippers? They are very common , so we forget that they are wonderful. They are very strong, but they open and close very easily. They come in many colours and sizes.In the 1890s, people in the United States wore high shoes with a long row of buttons. Clothes often had rows of buttons, too. People wished that clothes were easier to put on and take off.Whitcomb L.Judson, an engineer from the United States, invented the zipper in 1893. However, his zippers didn’t stay closed very well. This was embarrassing, and people didn’t buy many of them. Then Dr. Gideon Sundback from Sweden solved this problem. His zipper stayed closed.A zipper has three parts:1. There are dozens of metal or plastic hooks (called teeth) in two rows.2. These hooks are fastened to(固定于) two strips of cloth. The cloth strips are flexible. They bend easily.3. A fastener（扣件）slides along and joins the hooks together. When it slides the other way, it takes the hooks apart.Dr. Sundback put the hooks on strips of cloth. The cloth holds all the hooks in place. They didn’t come apart very easily. This solved the problem of the first zippers.I. VocabularyA. Match each word with the right picture.1. button ______2. a strip of cloth ______3. bend ______4. zipper ______A B. C.DB. Put the right word in each blank. The sentences are from the text.zipper embarrassing hooks dozenssolved bend fastened apart1. Reading for fun1.In the 1890s, people in the United States wore high shoes with a long __________ of buttons.2.There are __________ of metal or plastic __________ (called teeth) in two rows.3.The __________ is a wonderful invention.4. A fastener __________ along and joins the hooks together.5.Whitcomb L.Judson, an __________ from the United States, invented the zipper in 1893.6.When it slides the other way, it takes the hooks __________.7.This was __________, and people didn’t buy many of them.8.They __________ easily.9.These hooks are __________ to two __________ of cloth.10.Then Dr. Gideon Sundback from Sweden __________ this problem.1. Icy roads are dangerous because cars __________ on them.2. Pam cut a piece of paper into five __________.3. Sometimes your face gets red when you feel __________.4. Do you like to __________ math problems?5. You can catch fish with a __________.6. Hooks, buttons, and zippers are all __________.7. American supermarkets sell eggs by the __________.8. Tony and George had an apartment together, but now they live __________.9. Students sit in a circle in some classes. They sit in __________ in others.10. You __________ your knees when you sit down.11. Most pants and jackets have __________.12. An __________ knows how to build a road.D. Match each word with the right sound and Chinese meaning.Write the correct number or letter inSoundII. Reading comprehensionA. Choose the best answer.() 1. The zipper was invented in ______. (★)A. 1890B. 1893C. 1980D. 1983 () 2. Mr. Judson didn’t sell many zippers because ______. (★)A. they were hard to open and closeB. people liked rows of buttonsC. they came open very easilyD. they had cloth strips() 3. A zipper has ______ strips of cloth. (★)A. oneB. twoC. threeD. four () 4. The underlined word in the third paragraph “solve” means ______. (★★)A. work outB. look outC. find outD. pick out () 5. Which of the following statement is true? (★★)A. The hooks on zipper are cloth.B. Mr. Judson was from Sweden.C. Dr. Sundback invented the button hook.D. Zippers always come apart very easily.() 6. The passage is mainly about ______. (★★★)A. a zipper has hooks, cloth strips, and a slide fastenerB. people didn’t like the first zippersC. Mr. Judon and Dr. Sundback gave us a wonderful invention, the zipperD. zippers are one of the most useful inventions一、名词的分类类别意义例词专有名词表示人、地方、组织结构或事物等专有的名称Paris, Britain, the Great Wall, John 普通名词可数名词个体名词表示个别人和事物的名称 apple, lawyer, dictionary 集体名词表示若干人和事物的总称 class, family, people, police, team 不可数名词物质名词表示物质或材料的名称 bread, rice, water, milk, furniture 抽象名词表示性质、行为、状态和情感等抽象概念的名称happiness, weather二、名词的数 1) 规则变化 ① 一般名词后面加 smonth-months, bird-birds ② 以s, x, ch, sh 结尾的名词，后面加es classes, boxes, matches ③ 以o 结尾的名词，有的加es （有生命的）有的加s （无生命的）heroes, tomatoes, potatoesradios, zoos, bamboos, pianos, photos④ 以辅音字母加y 结尾的名词，变y 为i 再加es cities, countries, parties, factories ⑤ 以f 或fe 结尾的名词，变f 或fe 为v 再加esknife-knives, wolf-wolves ，scarf-scarves 例外：roof-roofs, chief-chiefs2）不规则变化单复数同形 sheep, fish, deer, Chinese, Japanese 元音变化 man-men, tooth-teeth, foot -feet, goose-geese 其他形式child-children, mouse-mice man 与woman 作定语修饰的名词改为复数时，两two women doctors, ten men drivers2. 语法:名词Presentation（1）单数变复数记忆口诀：单数变为复数式，后加s统言之。

初中英语新世纪教材八年级第一学期U1L1课时练习

Unit One Modern TechnologyLesson One ComputersⅠFill in the blanks with the words in their proper forms. (用所给单词适当形式填空)1.We can do word ________ (process) and surf the Internet on the computer.2.We can use the keyboard for ________(type) in information.3.Look！Two ________(mouse) are fighting for food over there.4.Price ought to ________ (come) down soon.5.The traffic lights are _______ (control) by a central computer.ⅡChoose the best answer(选择最恰当的答案)（）1. Please type ________ the file name, then press “Return”.A. toB. inC. ofD. for（）2. We must get familiar _________ the computer software we use.A. withB. toC. inD. on（）3. If he started out at nine, he ought to ________ here by now.A. wasB. beingC. beenD. be（）4. The details of today’s flights are displayed on the _________.A. mouseB. monitorC. electronicD. keyboard（）5. - _______ can you do with the mouse?- We can use it to control the computer.A. HowB. WhereC. WhichD. What（）6. We can stop us from _________ if we want to go?A. goB. to goC. goingD. goes（）7. Mary will help us _________ some of the organization.A. toB. withC. forD. at（）8.They allowed her _________ to the party.A. to goB. to goingC. of goD. of going（）9. The boss gave the _________ that the project should be finished before the end of this year.A. advicesB. orderC. helpD. advantage（）10. The computer is a significant __________ of recent decades.A. attentionB. nationC. connectionD. inventionⅢ. Choose the best answer(选择最恰当的答案)（）1. Could you tell me if he _________ finish the work on time?A. couldB. was able toC. is able toD. would be able to （）2. I am afraid that I ________ finish the task in such a short time. Could you help me, please?A. canB. am not able toC. am going toD. is able to（）3. – We need to make different kinds of food.-- My father is a good cook. He _______ help us.A. canB. is able toC. mayD. will（）4. – Why don’t you ask Tom to do it?-- I don’t know whether he is _______ to. He sometimes makes things worse.A. badB. ableC. afraid.D. easy（）5. I hope to _______ go shopping with you on Sunday.A. canB. mustC. mayD. be able to（）6. He is always trying his best to practice English and now he _______ speak English well. A. is able to B. mustn’t C. may D. has to（）7. Millie is free this weekend. She ________ watch the game show on TV on Sunday.A. ought toB. needC. mightD. has to（）8. Since you can’t work out this problem, you ________ go and ask Millie, she _________ know the answer.A. can; needB. need; mustC. can; mayD. must; mayⅢ.Put the following into English.(将下列词组译成英文)1. 网上购物___________________2. （计算机的）主机___________________3. 应当，应该___________________4. 与……连接在一起___________________5. 进行文字处理___________________6.阻止某人做某事___________________7. （渐渐）熟悉___________________ 8. 帮助某人做某事___________________9. （用键盘）输入，键入___________________ 10. 能，会（做）……___________________Ⅳ. Rewrite the sentences as required(按要求改写句子)1.Jack was able to surf the Internet on the computer. (改为疑问句)_________ Jack _________ to surf the Internet on the computer?2.I don’t know how to use all the food that’s left over.(保持原句意思)I don’t know _________ _________ _________ _________ all the food that’s left over.3.The fire-engine will come in ten minutes.(对划线部分提问)_________ _________ will the fire-engine come?4.We shan’t hold our school sports meeting next Monday. (改为被动语态)Our school sports meeting _________ be _________ next Monday.Ⅴ. Choose the best answer(选择最恰当的答案)（）1. – What’s the use ________ this robot?-- We can use it to clean our rooms.A. atB. ofC. onD. with（）2. --Look at the boy running on the ground. Is it David?--It __________ be him. I saw him go to the teachers’ office just now.A. mustB. can’tC. couldD. might（）3. – Mum , ________ I play computer games?-- Yes, you can. But you have to finish your homework first.A. mustB. willC. mayD. need（）4. – Must I finish that work today?-- No, you _________. You may finish it in three days.A. mustn’tB. shouldn’tC. couldn’tD. needn’t（）5. – Could I borrow your dictionary?-- Of course you __________.A. canB. mustC. shouldD. willU1L1I.Choices( ) 1. We can get more ____ about the international affairs on the Internet than before.A. informationB. bookC. reportD. progress( ) 2. No matter how hard the work is, we will keep ______ until we make it.A. tryB. tryingC. to tryD. tried( ) 3. I _______ the shop assistant 130 dollars for the mobile phone.A. paidB. spentC. costD. took( ) 4. The picture was painted by a famous young man. What do you think of modern art? The underlined part means ______.A. oldB. newC. ancientD. elder( ) 5. What do you think of ________ result of your project?A. aB. anC. theD. /( ) 6. He is a careful person. He always asks ______ some questions before making a decision.A. heB. himC. hisD. himself( ) 7. Fewer and fewer people choose to keep in touch with their friends by ordinary mail. Which is the closest in meaning to the underlined part?A. travelB. agreeC. communicateD. read( ) 8. We won’t go wrong, because I’m quite _____ the streets here.A. afraid ofB. proud ofC. familiar withD. careful with( ) 9. The heavy rain kept the children from playing outside. The underlined part means “________”.A. told…fromB. stopped…fromC. kept…offD. kept…in( ) 10. Qian Xuesen _______ many years doing research work at universities in the USA.A. costB. spentC. paidD. took( ) 11. People use the keyboard to ______ information.A. types inB. typed inC. type toD. type in( ) 12. –What’s the use ______ the Internet?--It shows words, pictures and so on.A. forB. ofC. toD. with( ) 13. The Internet _______ us ______ get more information.A. enable; toB. enabled; forC. enables; toD. able; to( ) 14. Tim’s father is very _______ about his health.A. worriedB. worryedC. worryD. worrying( ) 15. Some of the students are in favour of keeping pets at home. The underlined part means ______.A. are fond ofB. would like toC. prefers toD. agree with( ) 16. When the teacher is angry, the students will be quiet. The underlined part means ________.A. afraidB. carefulC. sadD. calmplete the sentences with the given words.1.Nowadays, computers are ________(wide) used in different fields.2.Good listening and speaking skills are key to _________(communication) with people fromdifferent countries.3.English newspapers and magazines are good for us to learn English. In ______(add), goodEnglish programs are helpful in learning English.4.Hen’s father works as a general manager in a _______(Germany) company in Shanghai.5.English is one of the ________(work) languages of the United Nations.III.Rewrite the following sentences as required.1.I got up early so that I could catch the train.(保持原句意思)I got up early _______ _______ to catch the train.2. A year has passed. Mr. Black came to work in Shanghai. (合并成一句)It _______ a year ________ Mr. Black came to work in Shanghai.3.We’ll come back in two days. (对划线部分提问)______ _______ will you come back?4.They had a discussion on water pollution last Friday. (改为否定句)They ______ _______ a discussion on water pollution last Friday.5.Sue listens to the English news to develop her listening skills. (对划线部分提问)_______ ________ Sue do to develop her listening skills?U1L1 Part 2 V ocabulary and Grammar (第二部分词汇与语法)I．Choose the best answer .(选择最恰当的答案) （共10分）（）1. In the computer shop, the shop assistant gave us _______ introduction about this new kind of computer .A. aB. anC. theD. /( ) 2. Please clean the _______ of your computer. It may be bad for your eyes.A. keyboardB. screenC. mouseD. monitor( ) 3. There is something wrong with my co mputer. It’s difficult to _______ the Internet.A. click onB. connect toC. take upD. pay for( ) 4. —— How does Jack _______ his goals?——He works hard.A. masterB. controlC. arriveD. achieve( ) 5. ——You mean you can’t get along well with your classmates?You’d better communicate with them more .——OK. I ______.A. willB. won’tC. ought toD. am able to（） 6. ——What do you call this in English ?——It’s a stamp .It ______ sending letters.A .is used for B. is used to C. is used as D. is used by( ) 7. ——Do you know who _______this movie ?——I don’t know. Oh, maybe it is Zhang Yimou .A. foundB. inventedC. directedD. created( ) 8. ——How can we learn more about the earth and the universe ?——More satellites ________ into space.A. must sendB. must be sentC. must have sentD. may send( ) 9. ——Why do we call the world “Global Village” ?——Because computers have made the world _______ , like a “village” .A. become smallerB. become biggerC. look like a ballD. stop growing( ) 10. ——Nick，I am sorry I broke your cup when you were away this morning .——________ .A. That’s all rightB. It’s a pleasureC. You are welcomeD. With pleasureplete the sentences with the given words in their proper forms .(用所给单词的适当形式填空) (共6分)1.We will be able _______ (do) anything as long as we work hard .2.My parents don’t allow me _________ (play) computer games too much.3.Edison was a great inventor. He had over 1,000 _______ (invent) during his life.4.Jim was able to ________ (swim) when he was five years old.5.I think the new technology has many ________ （advantage）. For example, computers are bad for our health.puters are used __________ (control) not only the speed but also the direction of the spaceships .IV. Rewrite the sentences as required. (按要求改写句子，每空格限填一词)1. Scientists make computers serve our lives better. (改为被动语态)Computers ________ _______ ________ serve our lives better.2. Please tell him to go there alone. (改为否定句)Please tell him _________ ___________ __________ there alone3. She was heard to sing by her classmates in the classroom（对画线部分提问）Where __________ she _________ to sing by her classmates?4.There are more than 70 different kinds of computer companies .(对画线部分提问)________ _________ different kinds of computer companies are there5. Both Lucy and Lily have been to the Great Wall .(改为否定句)_________ Lucy ________ Lily ________ been to the Great Wall.6. My little sister could surf the Internet when she was six years old . (改为同义句)My little sister _______ ________ _________ surf the Internet when she was six years old .。

【单元练】《易错题》初中九年级物理第十六章【电压和电阻】知识点复习(培优练)

一、选择题1．关于金属导体的电阻，下列说法正确的是（）A．当导体两端的电压和通过导体的电流为零时，导体的电阻为零B．当导体被均匀拉长时，它的电阻会逐渐减小C．不管什么条件下，铝和铅的电阻都不会变成零D．在长度、横截面积和温度都相同时，铁导线比铜导线的电阻大D解析：DA．导体的电阻跟导体两端的电压和通过导体的电流没有任何关系，故A错误；B．导体的电阻与导体的长度成正比，材料、横截面积和温度相同时，长度越长，电阻越大，故B错误；C．铝在-271.76°C以下，铅在-265.95°C以下时，电阻就变成了零，故C错误；D．导体的电阻与材料、长度、横截面积和温度有关，在其他条件相同时，铁导线比铜导线的电阻大，故D正确。

故选D。

2．小华用如图所示的电路研究串联电路特点，电源电压保持不变。

闭合开关S，两电表中只有一个电表有示数，将L1和L2交换位置，再闭合开关，两电表均有示数。

已知电路中除了L1、L2外，其它电路元件均完好。

下列说法正确的是（）A．可以确定，只有L1短路B．可以确定，只有L1断路C．可以确定，L1短路且L2断路D．可以确定，L1断路且L2短路A解析：A由电路可知两灯串联，电压表测L1两端电压。

若电路中L1或者L2断路，两者交换位置后，电路中依然无电流，即电流表始终没有示数，所以两灯均不可能断路；若L1短路，则电流表有示数，电压表被短路无示数，交换两灯位置后电流表和电压表均有示数。

故BCD 错误，A正确。

故选A。

3．已知R1∶R2=4∶3，将它们接在如图所示的电路中，电源电压为6V的，闭合开关S。

则通过它们的电流之比及它们两端的电压之比是（）A．I1：I2=3：4 U1：U2=1：1B．I1：I2=3： 4 U1：U2=3：4C．I1：I2=4：3 U1：U2=1：1D．I1：I2=1：1 U1：U2=4：3A解析：A由于并联电路电压相等，由图知道，它们并联在同一电路中，所以，它们两端的电压之比为1：1；由UIR=知道，通过它们的电流之比1122123=4UI R RUI RR==综上所述，只有A正确。

二端口网络

若二端口的Y参数不仅有Y12 = Y21，而且还有 Y11=Y22，则这样的二端口在电气上是对称的，称为对称二端口，它只有2个参数是独立的。
把对称二端口的两个端口互换位置后与外电路连接，外部特性不会有任何变化。
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I.2 U2
. =Yb+Yc
U1=0
元件构成的任何无源二端口，都具有互易性质，所以Y21=Y12。
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10
关于二端口的对称性
满足互易性质的二端口，只有3个参数是独立的。
之间的开路转移阻抗。
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2-2'的输入阻抗。 12
把Z参数方程写成矩阵形式：比较可知：
. U.1 = Z11 Z12 U2 Z21 Z22
.
.
I.1 = Z I.1
I2
I2
开路阻抗矩阵Z与短路结束导纳矩阵Y存在互为逆阵的关系：
可得Z(阻抗)参数矩阵
def
Z
Z11 Z12
Z21 Z22
3
注意
如果组成二端口网络的元件都是线性的，则称
结束
为线性二端口网络；
依据二端口网络的二个端口是否服从互易定理，分为可逆的和不可逆的；
依据二端口网络使用时二个端口互换是否不改变其外电路的工作情况，分为对称的和不对称的。

微机保护的算法

的采样瞬间的中间值。
in+1
in Ts
Ts
n t1 n+1
t1
t2
in+2 n+2
DD21inin21TTssiinn1
，
i1
in
in1 2
i2
in1
in2 2
，
u1
un
un1 2
u2
un1
un2 2
（3—48)
（2）积分法
对（3—44)分别三章微机保护的算法
3.1概述
常规保护把被测信号
引入保护继电器，继电器
Φ
按照电磁、感应、比幅、比相等原理作出动作与否 I
的判断。
微机保护把经过数据采集系统量化的数字信号经
过适当的算法，计算出交流信号的有效值、相位以及多个信号的组合量如：阻抗、相位等。
算法定义：
• 微机保护装置根据模数转换器提供的输入电气量的采样数据进行分析、运算和判断，以实现各种继电保护功能的方法称为算法。
• 是研究由若干个采样数据求取保护原理所需要的故障特征量的方法
算法分类：
• 直接由采样值经过某种运算，求出被测信号的实际值再与定值比较。
• 依据继电器的动作方程，将采样值或由它们计算出的中间变量代入动作方程，转换为运算式的判断。
算法目的：
• 算法的核心是求出表征被保护对象运行特点的物理量，如：电压、电流的有效值和相位以及视在阻抗等，或者算出它们的序分量、基波分量、某次谐波分量的大小和相位等。
， D di
dt
（3—46)
注：为例满足独立方程的需要，要求
t1
t2
k
T 2
(k
0,1, 2,3