测量电源的电动势和内阻

测量电源的电动势和内阻 一、伏安法 电路图:有两种连接方式，如图1所示电流内接法和如图2所示的电流表外接法。 原理:闭合电路欧姆定律，改变外电阻R，就能测得U、I的数据，利用两组数据代入公式可求得E、r的数值，但误差较大，通常利用多组数据作出U—I图象来求解。 误差:利用如图1所示的电路测量时，E,E，r,r; 测真测真 利用如图2所示的电路测量时，E=E，r,r。 测真测真 例1[2014?北京卷]利用电流表和电压表测定一节干电池的电动势和内电阻(要求尽量减小实验误差( ”或“乙”)( (1)应该选择的实验电路是图1中的________(选填“甲 甲 乙 图1 (2)现有电流表(0,0.6 A) 、开关和导线若干，以及以下器材: A. 电压表(0,15 V) B. 电压表(0,3 V) C. 滑动变阻器(0,50 Ω) D. 滑动变阻器(0,500 Ω) 实验中电压表应选用________;滑动变阻器应选用________((选填相应器材前的字母) (3) 某位同学的6组数据如下表所示，其中5组数据的对应点已经标在图2的坐标纸上，请标出余下一组数据的对应点，并画出U-I图线. 序号 1 2 3 4 5 6 电压U(V) 1.45 1.40 1.30 1.25 1.20 1.10 电流I(A) 0.060 0.120 0.240 0.260 0.360 0.480 design of urban bridge (CJJ 11-2011), General specification for design of highway bridges and culverts (JTG D60-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2004) of the highway bridge design specifications for masonry (JTG D61-2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course code: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small-class teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' practical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system of underground space and its supporting. To ensure 图2 (4)根据(3)中所画图线可得出干电池的电动势E,________V，内电阻r,________Ω. (5)实验中，随着滑动变阻器滑片的移动，电压表的示数U及干电池的输出功率P都会发生变化(图3的各示意图中正确反映P-U关系的是________( A B C D 图3 【例2】 [2014?全国卷] 现要测量某电源的电动势和内阻(可利用的器材有:电流表A，内阻为1.00 Ω; 电压表V;阻值未知的定值电阻R、R、R、R、R;开关S;一端连有12345 鳄鱼夹P的导线1，其他导线若干(某同学的测量电路如图(a)所示( (1)按图(a)在实物图(b)中画出连线，并标出导线1和其P端( 图(a) 图(b) (2)测量时，改变鳄鱼夹P所夹的位置，使R、R、R、R、R依次串入电路，记录对12345 应的电压表的示数U和电流表的示数I. 数据如下表所示(根据表中数据，在图(c)中的坐标纸上将所缺数据点补充完整，并画出UI图线( I(mA) 193 153 111 69 30 U(V) 2.51 2.59 2.68 2.76 2.84 of undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' pracclass tea-g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11erground space and its supporting. To ensure2 图(c) (3)根据UI图线求出电源的电动势E,________V，内阻r,________Ω.(保留2位有效数字) 【例3】硅光电池是一种可将光能转换为电能的器件。某同学用题22图2所示电路探究硅光电池的路端电压U与总电流I的关系。图中R为已知定值电阻。电压表视为理想电压表。 ?请根据题22图2，用笔画线代替导线将题22图3中的实验器材连接成实验电路。 VU?若电压表的读数为，则I= 20 ?实验一:用一定强度的光照 射硅光电池，调节滑动变阻器，通 过测量得到该电池的U-I曲线a。见 题22图4，由此可知电池内阻 (填“是”或“不是”)常数，短路 电流为 mA ，电动势为 V. ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condits ' practical skills. Through this module students learn can master the skills of maintenanclass teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-njunction with training courses, smallin co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 113 ?实验二:减小实验一中光的强度，重复实验，测得U-I曲线b，见题22图4. 当滑动变阻器的电阻为某值时，若实验一中的路端电压为1.5V。刚实验二中外电路消耗的电功率为 mW(计算结果保留两位有效数字)。 变式一,没有电压表，利用小量程的电流表和定值电阻改装成电压表。 例4、在测定一节干电池的电动势和内电阻的实验中，备有下列器材:干电池(电动势E约为1(5V，内电阻r约为1(0Ω);电流表G(满偏电流3(0mA，内阻R=10Ω);g电流表A(量程0,0(6A，内阻约为0(5Ω);滑动变阻器R(0,20Ω，10A);滑动变阻 ‘器R(0,100Ω，1A);定值电阻R=990Ω;开关和导线若干。 3 (1)为了能准确地进行测量，也为了操作方便，实验中应选用的滑动变阻器是_________。(填写数字代号) (2)请画出实验原理图。 (3)电源的电动势E= 内阻r= 变式二,没有电压表，利用已知内阻的电流表代替电压表来测电压。 例5、 用一块内阻已知的电流表和一块内阻未知的电流表可以测量内阻较大的电源 的电动势和内电阻，其电路原理图如图5所示。设A的内电阻为R，假设两电流表的总量10 程略大于所在回路的电流，若S闭合，S断开时，电流表A的示数为I，S闭合时，两表12112的读数分别为和。则有电源的电动势E= 内阻r= ,,II12 二、安阻法 电路图:如图6所示。 erground space and its supporting. To ensureof undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' pracclass tea-g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 114 原理:由闭合电路欧姆定律。改变电阻箱的阻值R就能得到R、I数据，利用两组数据就能求得E、r，或利用多组数据作图象来求解。 误差:E=E，r,r 测真测真 例6、[2014?新课标全国卷?] 利用如图(a)所示电路，可以测量电源的电动势和内阻，所用的实验器材有: 待测电源，电阻箱R(最大阻值999.9 Ω)，电阻R(阻值为3.0 Ω)，电阻R(阻值为3.0 Ω)，01电流表A(量程为200 mA，内阻为R,6.0 Ω)，开关S. A 实验步骤如下: ?将电阻箱阻值调到最大，闭合开关S; ?多次调节电阻箱，记下电流表的示数I和电阻值箱相应的 阻值R; 11?以为纵坐标，R为横坐标，作 ?R图线(用直线拟合); II ?求出直线的斜率k和在纵轴上的截距b. 1 (1)分别用E和r表示电源的电动势和内阻，则与R的关系式为________( I (2)实验得到的部分数据如下表所示，其中电阻R,3.0 Ω时电流表的示数如图(b)所示，读出数据，完成下表(答:?________，?________( R/Ω 1.0 2.0 3.0 4.0 5.0 6.0 7.0 ? I/A 0.143 0.125 0.100 0.091 0.084 0.077 ,1,1I/A ? 6.99 8.00 10.0 11.0 11.9 13.0 ,1(3)在图(c)的坐标纸上将所缺数据点补充完整并作图，根据图线求得斜率k,________AΩ,1,1，截距b,________A. (4)根据图线求得电源电动势E,________V，内阻r,________Ω. in co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condits ' practical skills. Through this module students learn can master the skills of maintenanclass teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-njunction with training courses, small5 例7、请从下列器材中选择适当仪器设计一个电路，要求用此电路既能测量待测电阻Rx的电阻(约500Ω)，又能测量电源E的电动势。 a(待测定值电阻R:阻值约500Ω x b(滑动变阻器R:总阻值1000Ω 1 c(电阻箱R:最大阻值999(9Ω 2 :最大阻值99 d(电阻箱R(9Ω 3 e(电流表A:量程3mA，内阻约50Ω f(电源E:电动势约为3V，内阻很小但不可忽略 g(单刀双掷开关及导线若干 (1)实验中应选取的器材有: (填写器材前面的字母序号) (2)请在虚线框中画出实验电路图 (3)在测出电阻R的值后(记为R)，再利用此电路测量电源E的电动势。还需用xx 测量的物理量有: ，用所测的物理量表示电源E的电动势 。 为 三、伏阻法 电路图:如图13所示。 原理:由闭合电路欧姆定律。改变电阻箱的阻值 R就能得到R、U数据，利用两组数据就能求得E、r。但误差较大，通常利用多组数据作出U—I图象来求解。 误差:E,E，r,r 测真测真 例8、(2012福建卷)(12分)某研究性学习组欲测定一块电池的电动势E。 ?先直接用多用电表测定该电池电动势。在操作无误的情况下，多用电表表盘示数如图，其示数为____V。 R?然后，用电压表、电阻箱R、定值电阻、开关S、若干导线和该电池组成电路，0 测定该电池电动势。 erground space and its supporting. To ensureof undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' pracclass tea-g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 116 (?)根据电路图，用笔画线代替导线，将实物图连接成完整电路。 (?)闭合开关S，调整电阻箱阻值R，读出电压表相应示数U。该学习小组测出大量数据，分析筛选出下表所示的R、U数据，并计算出相应的1/R与1/U的值。请用表中数据在坐标纸上描点，并作出1/U-1/R图线。 例9(2008年全国卷?)一直流电压表，量程为1 V，内阻为1000Ω。现将一阻值为5000,7000Ω之间的固定电阻R与此电压表串联，以扩大电压表的量程。为求得扩大后量1 程的准确值，再给定一直流电源(电动势E为6,7 V，内阻可忽略不计)，一阻值R=20002Ω的固定电阻，两个单刀开关SS及若干导线。 1( 2 (1)为达到上述目的，将答题卡上对应的图连成一个完整的实验电路图。 (2)连线完成以后，当S与S均闭合时，电压表的示数为0(90 V;当S闭合，S1212断开时，电压表的示数为0(70 V。由此可以计算出改装后电压表的量程为 V，电源电动势为 V。 例10、为了测量两节串联干电池的电动势，某同学设计了如图16所示的实验电路，其中E是待测电池组，内阻不能忽略;V、是两只量程都合适的电表，内阻不是很大，且12 未知，S、S是单刀单掷开关;导线若干。 12 class teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-njunction with training courses, smallin co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condits ' practical skills. Through this module students learn can master the skills of maintenan7 (1)请根据电路图甲，在图乙中连线，将器材连成实验电路。 (2)实验需要测量的物理量是 。 (3)用测出的物理量，导出串联电池组电动势的表达式是 。 【例1】(1) 甲 (2)B C (3)略 (4)1.50(1.49，1.51) 0.83(0.81，0.85) (5)C [解析] 第(1)问考查电流表的内外接法,第(2)问考查仪器的选择,第(3)问考查作图～数据处理,第(4)问考查图像,第(5)问考查输出功率( (1)根据U,E,Ir测量电源电动势和内阻时～需要测出多组对应的路端电压U和干路电流I ～电压表和电流表内阻影响会造成实验误差(电源内阻较小～所以电流表分压影响较大～因此应选择甲电路( (3)略( (4)根据U-I图像～电源的电动势等于纵轴的截距～内阻为斜率的绝对值( E,U1E2,,(5)电源输出功率P,UI,U,,U，U～P-U 图像为开口向下的二次函数～,,rrr 应选 C. 【例2】(1)连接如图所示( (2)UI图线略( (3)2.90(在2.89,2.91之间均给分) 1.03(在0.93, 1.13之间均给分) [解析] 本题考查电源电动势和内电阻的测量( (1)实物连线要注意连接主干电路～最后再连接电压 表((2)根据坐标纸上描出的各点～连接成一条直线～尽 量使得各点对称分布在直线两旁( (3)图像直线纵轴截距表示电源电动势，斜率绝对值表示电源内电阻( 【例3】答案: erground space and its supporting. To ensureof undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' pracclass tea-g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 118 【例4】解析:由闭合电路欧姆定律可知，只要能测出两组路端电压和电流 的内阻已知，可以把内阻已知的电流即可，但题目中只给出两个电流表且其中一个电流表G 表和定值电阻R串联改装成一个电压表。为了减少误差，滑动变阻器应选R，设计实验原理3 图如图4所示。 分别测两组电流表G和A的读数，则有: 可得:， 点评:此方法能准确地测量出电源的电动势和内阻，无系统误差。 【例5】、当S闭合时，有: 1 ， 当S闭合时，有: 2 ， ts ' practical skills. Through this module students learn can master the skills of maintenanclass teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-njunction with training courses, smallin co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condi9 联立以上两式可得电源的电动势和内电阻分别为:， 点评:此方法亦能准确地测量出电源的电动势和内阻，无系统误差。 R，R，RR11A1A1，，【例6】((1),R，R，(r，R) A0，，IERER11 (2)0.110 9.09 (3)1.0(或在0.96,1.04)之间，6.0(或在5.9,6.1之间) (4)3.0(或在2.7,3.3之间)，1.0(或在0.6,1.4之间) [解析] 本题考查了测量电源电动势和内电阻的实验((1)根据闭合电路欧姆定律有 IRA,,E,，I(R，R，r)，IR. 0A,,R1 代入数据～化简得 ,R，R,R，R11A1A1，，,R，,R，r,，R. 0A，，IERER11,1(2)电流表每小格表示4 mA～因此电流表读数是0.110 A～倒数是9.09 A. ,1,1(3)根据坐标纸上给出的点～画出一条直线～得出斜率k,1.0 A?Ω～截距b,6.0 A,1. R，R，RR1bEA1A1，，(4)斜率k,～因此E,3.0 V～截距b,R，,r，R,～因此r,,5A0，，ERER311 ,1.0 Ω. 【例7】 解析:(1)a、b、c、e、f、g (2)如图12所示 class tea-g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11erground space and its supporting. To ensureof undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' prac10 (3)解法一:开关接2，调节变阻器R至适当位置并保持不变，调节电阻箱R，记录12 ’‘电阻箱读数R和电流表读数I，再次调节电阻箱R，记录电阻箱读数R和电流表读数I，222则 由上两式可得 解法二:开关接1，调节变阻器R至适当位置并保持不变，记录电流表读数I，开关接112，调节电阻箱R，记录电阻箱读数R和电流表读数I，则 222 由上两式可得。 【例8】答案: ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condits ' practical skills. Through this module students learn can master the skills of maintenanclass teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-njunction with training courses, smallin co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 1111 【例9】 解析:(1)连线如图15所示。 (2)设电压表的内阻为R。当S与S均闭合时，电压表的示数U=0(90 V，则 V121 当S闭合，S断开时，电压表的示数U= 0(70 V，则 122 联立以上两式可得:R=6000Ω，E=6(3V。 1 erground space and its supporting. To ensureof undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' pracclass tea-g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 1112 改装后电压表的量程为:。 变式:利用两只电压表，既测电压又当电阻，测电源的电动势和内阻。 【例10】解析:(1)实物连线图如图17所示。 ‘ (2)先闭合S，断开S时，V的读数U ，V的读数U;再闭合S时，V的读数U。 121121211 (3)设V的内阻为R，由闭合电路欧姆定律得， 1V1 当闭合S，断开S时， 12 再闭合S时， 2 联立以上两式可得:，。 点评:用这种方法能准确地测出电源的电动势，若再已知电压表V的内阻还可以准确1地测量出电源的内阻，无系统误差。 二、特殊测量方法 1(利用辅助电源测量 njunction with training courses, smallin co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condits ' practical skills. Through this module students learn can master the skills of maintenanclass teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-13 电路图:如图18所示。 ’ 原理:调节滑动变阻器R和R，使电流表G的示数为0，此时A(B两点的电势φφA(B的关系是φ=φ，读出电流表A和电压表V的示数I和U，则，利用两组数据可AB 求得E、r的数值。 误差:此方法无系统误差，精确程度取决于电流表G的灵敏程度。 ’ 例9 某小组设计了如图18所示的电路，该电路能够测量电源的电动势E和内阻r，E是辅助电源，A、B两点间有一灵敏电流表G。 (1)补充下列实验步骤: ?闭合开关S、S， 使得灵敏电流表的示数为零，这时，A、B12 两点的电势φ、φ的关系是φ φ，即相当于同一点，读出电流表和电压表的示数ABAB I和U，其中I就是通过电源E的电流。 111 ‘ ?改变滑动变阻器R、R的阻值，重新使得 ，读出 (2)写出步骤?、?对应的方程式及电动势和内阻的表达式。 ‘ 解析:(1)?闭合开关S、S，调整滑动变阻器R、R的阻值使得灵敏电流表的示数12 为零时，A、B两点的电势φ、φ相等。 AB ‘ ?改变滑动变阻器R、R的阻值，重新使得灵敏电流表的示数为零，读出电流表和电压表的示数I和U。 22 (2)当灵敏电流表的示数为零时，由闭合电路欧姆定律得 erground space and its supporting. To ensureof undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' pracclass tea-g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 1114 联立以上两式得 电流表的电压表的示数I和U时， 11 电流表的电压表的示数I和U时， 22 可解得，。 2(利用电桥平衡测量 电路图:如图19所示。 原理:调节变阻器R和R使电流表G的读数为0，此时电流表A和A的示数之和就是1212流过电源的电流I(即干路电流)，电压表V和V的示数之和就是电源的路端电压U，则12 ，两次调节R和R，使电流表G的示数变为0，读出四个电表的读数，便可求12 出电源电动势和内阻。假设第一次两电流表示数之和为I，两电压表示数之和为U，则11 ;第二次两电流表示数之和为I，两电压表示数之和为U，则，22联立可得，。 误差:此方法同样无系统误差，并且不必考虑电表带来的误差，因为此时电表相当于电 源的外电路电阻，精确程度取决于电流表G的灵敏程度。 3(利用电动势已知的电源测某电源的电动势 电路图:如图20所示。 class teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-njunction with training courses, smallin co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condits ' practical skills. Through this module students learn can master the skills of maintenan15 原理:图20中E为供电电源，E为为标准电源，E为待测电源，R是限流电阻，r电sxp0流表G的保护电阻。测量时，首先闭合开关S，电阻丝AB上有一定的电势降落;接着将开1 关S合到“1”位置，移动滑动触头C，使G指针指零，此时AC的长度为L，AC段电压为21E;再将S合到“2”位置，移动滑动触头C，使G指针再指零，此时AC的长度为L，AC段s22电压为E。由于电流表G的示数为0，则两次流过AB的电流不变，故，x 得。 误差:此实验无系统误差，精确程度取决于电流表G的灵敏程度。 例6 如图20所示的电路可测电源的电动势，图中E为供电电源，E为为标准电源，sE为待测电源，R是限流电阻，r电流表G的保护电阻。测量时，首先闭合开关S，电阻丝xp01AB上有一定的电势降落;接着将开关S合到“1”位置，移动滑动触头C，使G指针指零，2 此时AC的长度为L;再将S合到“2”位置，移动滑动触头C，使G指针再指零，此时AC12 的长度为L。 2 (1)若仅闭合S时流过AB的电流为I，那么当S分别合到“1”、“2”上后，通过102 滑动触头C，使G指针指零时，流过AC段的电流分别是 和 。 (2)由题中的已知量求得待测电源的电动势E= 。 x 解析:(1)因为G指针指零时，流过r的电流为零，则S无论是接“1”还是接“2”，02 流过AC段的电流均是I。 0 (2)设AB的长度为L，则 -g of this module is to the automotive air conditioning repair class teaching in conjunction with training courses, small1, course, course: this course is a professional course of automobile maintenance and testing specialty. 2, task: the teachin de: 3, credits/units: 160 hours 4, major: automobile maintenance and testing specialty second nature and task2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-for masonry (JTG D61 2004) of the highway bridge design specifications-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11erground space and its supporting. To ensureof undapplication technologySummary of excavation of Foundation pit engineering below refers to the surface of a supporting system e, testing, analysis, judgement and skill to help troubleshoot auto air conditioning in common, which reflect the automobile ractictical skills. Through this module students learn can master the skills of maintenance of auto air conditioning; theory with pching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering students ' pracclass tea16 联立解得:。 class teaching and practical training in the teaching process, theory for sufficient degree, with a focus on fostering studen-njunction with training courses, smallin co nance and testing specialty. 2, task: the teaching of this module is to the automotive air conditioning repair class teachingnce and testing specialty second nature and task 1, course, course: this course is a professional course of automobile maintede: 3, credits/units: 160 hours 4, major: automobile maintena2005) code for design of highway bridge and culvert 1, course name: car air conditioning repair Mo Zhen, Editor 2, course co-004) of the highway bridge design specifications for masonry (JTG D612-2004) code for design of reinforced concrete and prestressed concrete Highway (JTG D62-2011), General specification for design of highway bridges and culverts (JTG D60-design of urban bridge (CJJ 11ers to the surface of a supporting system of underground space and its supporting. To ensureow reftioning in common, which reflect the automobile application technologySummary of excavation of Foundation pit engineering belce of auto air conditioning; theory with practice, testing, analysis, judgement and skill to help troubleshoot auto air condits ' practical skills. Through this module students learn can master the skills of maintenan17