《电路》第五版试题.doc

<p>目 &nbsp; &nbsp;录

第一章 &nbsp;电路模型和电路定律 1
第二章 &nbsp;电阻电路的等效变换 8
第三章 &nbsp;电阻电路的一般分析 17
第四章 &nbsp;电路定理 22
第五章 &nbsp;含有运算放大器的电阻电路 33
第六章 &nbsp;储能元件 39
第七章 &nbsp;一阶电路和二阶电路的时域分析 42
第八章 &nbsp;相量法 51
第九章 &nbsp;正弦稳态电路的分析 53
第十章 &nbsp;具有耦合电感的电路 74
第十一章 &nbsp;电路的频域响应 82
第十二章 &nbsp;三相电路 82
第十三章 &nbsp;非正弦周期电流电路和信号的频谱 96
第十四章 &nbsp;线性动态电路的复频域分析 96
第十六章 &nbsp;二端口网络 100
第十七章 &nbsp;非线性电路 39

第一章 &nbsp;电路模型和电路定律
一、是非题 (注:请在每小题后[ &nbsp;]内用&quot;√&quot;表示对,用&quot;×&quot;表示错) &nbsp;
.1. 电路理论分析的对象是电路模型而不是实际电路。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√]
.2. 欧姆定律可表示成U=RI,也可表示成U=-RI,这与采用的参考方向有关。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√] &nbsp;
.3. 在节点处各支路电流的方向不能均设为流向节点，否则将只有流入节
点的电流而无流出节点的电流。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×]
.4. 在电压近似不变的供电系统中，负载增加相当于负载电阻减少。 &nbsp; &nbsp; &nbsp; &nbsp; [√]
. &nbsp; 解：负载增加就是功率增加，。
5. &nbsp;理想电压源的端电压是由它本身确定的，与外电路无关，因此流过它的电流则是一定的，也与外电路无关。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×]
.6. 电压源在电路中一定是发出功率的。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×]
.7. 理想电流源中的电流是由它本身确定的，与外电路无关。因此它的端电压则是一定的，也与外电路无关。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×]
.8. 理想电流源的端电压为零。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×]
.9. *若某元件的伏安关系为u＝2i+4，则该元件为线性元件。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√]
. &nbsp; 解：要理解线性电路与线性元件的不同。
10.* 一个二端元件的伏安关系完全是由它本身所确定的，与它所接的外电路毫无关系。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[√]
.11.元件短路时的电压为零,其中电流不一定为零。元件开路时电流为零,其端电压不一定为零。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√]
.12. 判别一个元件是负载还是电源，是根据该元件上的电压实际极性和电流的实际方向是否一致（电流从正极流向负极）。当电压实际极性和电流的实际方向一致时，该元件是负载，在吸收功率；当电压实际极性和电流的实际方向相反时，该元件是电源
（含负电阻），在发出功率 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√] &nbsp;
.13.在计算电路的功率时，根据电压、电流的参考方向可选用相应的公式计算功率。若选用的公式不同,其结果有时为吸收功率，有时为产生功率。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[×]
.14.根据Ｐ=ＵＩ,对于额定值220V、40W的灯泡,由于其功率一定，电源电压越高则其电流必越小。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×] &nbsp;
.15.阻值不同的几个电阻相串联，阻值大的电阻消耗功率小。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×] &nbsp;
&nbsp; &nbsp;解：串联是通过同一电流，用。
.16.阻值不同的几个电阻相并联，阻值小的电阻消耗功率大。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√] &nbsp;
&nbsp; &nbsp;解：并联是承受同一电压，用。
.17.电路中任意两点的电压等于所取路径中各元件电压的代数和。而与所取路径无关。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√]
.18.当电路中的两点电位相等时,若两点间连接一条任意支路，则该支路电流一定为零。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×] &nbsp; &nbsp;
.19. 若把电路中原来电位为3V的一点改选为参考点,则电路中各点电位比原来降低３Ｖ,各元件电压不变。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√] &nbsp; &nbsp;
.20.电路中用短路线联接的两点电位相等,所以可以把短路线断开而对电路其他
部分没有影响。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×] &nbsp; &nbsp;
二、选择题 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(注:在每小题的备选答案中选择适合的答案编号填入该题空白处,多选或不选按选错论) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.1. 通常所说负载增加，是指负载__Ｃ__增加。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (Ａ) 电流 &nbsp; (Ｂ) 电压 &nbsp; (Ｃ) 功率 &nbsp; (Ｄ) 电阻 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.2. 图示电路中电压ＵAB为_Ｃ____V。
&nbsp; &nbsp; 解：
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(Ａ) 21 ； &nbsp; &nbsp; &nbsp;(Ｂ)16； &nbsp; &nbsp; &nbsp; &nbsp;
(Ｃ) -16； &nbsp; &nbsp; &nbsp;(Ｄ) 19 &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.3. 图示电路中，下列关系中正确的是_Ａ___。 &nbsp; &nbsp; &nbsp; &nbsp;
解： ,
&nbsp; &nbsp; ,或
（Ａ）Ｉ1+Ｉ2=Ｉ3； &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
（Ｂ）Ｉ1Ｒ1+Ｉ3Ｒ3+Ｅ1= 0； &nbsp;
（Ｃ）当Ｒ3开路时Ｕ=Ｅ2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.4. 图示电路中Ｓ断开时Ｉ1= _Ｃ_A, &nbsp; &nbsp; &nbsp; &nbsp;
Ｉ=_Ｂ_A。Ｓ闭合时Ｉ1= _Ａ_A,Ｉ=_Ｃ_A。
解：Ｓ断开时，没有通路，电流为零；
；
Ｓ闭合时，有通路，电流
电阻被短路，电压为零，。

(Ａ) 6 ； &nbsp;(Ｂ) 2 ； &nbsp;
(Ｃ) 0 ； &nbsp;(Ｄ) 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.5. 图示电路中,当ＩS=10A 时电压Ｕ为_Ｃ_V,当ＩS=8A时电压Ｕ为_Ｄ_V。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;解：当ＩS=10A 时,，
&nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;当ＩS=8A时, ,
&nbsp; &nbsp; &nbsp; &nbsp;
(Ａ) 0 ； &nbsp;(Ｂ) 8 ；
&nbsp;(Ｃ) 12； &nbsp;(Ｄ) 16 。 &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.6. 图示电路中 Ｉ = 0 时,电位 ＵA=_Ｂ_ V。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
解：Ｉ = 0 时,，
。
(Ａ) 70 V ； &nbsp; &nbsp;(Ｂ) 60 V ；
(Ｃ) -10 V ； &nbsp; (Ｄ) 90 V。 &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
三、填空题 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.1. 图示电路中电流Ｉ=_-3_Ａ。 &nbsp;
&nbsp; 解：

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

.2. 电路图中的IX = _1.4_ Ａ。 &nbsp; &nbsp; &nbsp;
&nbsp;解：

&nbsp; &nbsp; 。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

四、计算题 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
1. 求图示电路中的ＵX 、IX &nbsp; &nbsp; &nbsp; &nbsp;
解：

&nbsp; &nbsp; 。

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
2. 求如图所示电路中ＵS =?
解：标电流参考方向如下图
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; ； ，；
； &nbsp;。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
3. 求图示电路中的is &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
解：

。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

4. 图示电路中，求：
(1)当开关Ｋ合上及断开后，ＵAB=?
(2)当开关Ｋ断开后，ＵCD =?
解：
(1)当开关Ｋ合上，；
&nbsp; &nbsp;当开关Ｋ断开后，
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (2)当开关Ｋ断开后，。

5.求出图示电路的未知量Ｉ和Ｕ。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
解： &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;
6. *电路如附图所示。试求： &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(1)求电压u; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; │ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(2)如果原为1Ω、4Ω的电阻和1Ａ的电流源可以变动(可以为零,也可以为无限大)
对结果有无影响。 &nbsp; &nbsp;
解：(1)求电压u；
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;(2)如果原为1Ω、4Ω的电阻和1Ａ的
电流源可以变动(可以为零,也可以为无
限大) 对结果有无影响。 &nbsp; &nbsp;
&nbsp; 4Ω的电阻不为零，则对结果无影响。

7. 试求电路中各元件的功率。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; 解：标参考方向
&nbsp;
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;
8. 试求电路中负载所吸收的功率。
&nbsp;解：标参考方向

&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
9. 求图示电路中的电流Ｉ和受控源的输出功率。
解：

&nbsp; &nbsp;(实际吸收功率)。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
10. 电路如图所示。试求: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(1)仅用ＫＶＬ求各元件电压； &nbsp;
(2)仅用ＫＣＬ求各元件电流； &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(3)如使流经3伏电压源的电流
为零，则电流源iS 应为什么值。
解：电源取非关联的参考方向，
电阻取关联的参考方向。
(1) 仅用ＫＶＬ求各元件电压；
&nbsp;
,，
&nbsp;(2)仅用ＫＣＬ求各元件电流；
，，，，

(3)

11. 求图示电路中电源发出的功率. &nbsp;
&nbsp;解：电源取非关联的参考方向，
电阻取关联的参考方向。
&nbsp; &nbsp; &nbsp;， ，
&nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; ，
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
12. 如图，试计算ＵAC, ＵAD &nbsp; &nbsp; &nbsp;
&nbsp; 解：
&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp;

13.计算如图示电路中当开关Ｋ断开及接通时Ａ点的电位ＶA
&nbsp; &nbsp; 解：
&nbsp; &nbsp; 开关Ｋ断开时，
&nbsp; &nbsp;
开关Ｋ接通时，

14. 图示电路中,以Ａ点为参考点计算电位ＵC、ＵDＵE和电压ＵBE &nbsp; &nbsp;
解：
关键点：8Ω电阻中的电流为零。

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
15. 图中各电阻均为1Ω,则当ＵAB =5V时ＵS应为多少? &nbsp;
解：关键点：，

&nbsp;， &nbsp;

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 第二章 &nbsp;电阻电路的等效变换
一、是非题 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(注:请在每小题后[ &nbsp;]内用&quot;√&quot;表示对,用&quot;×&quot;表示错) &nbsp; &nbsp;
.1. 如图所示电路的等效电阻为 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√]
解：

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.2. 当Ｒ1、Ｒ2与Ｒ3并联时等效电阻为: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[×] &nbsp; &nbsp;
.3. 两只额定电压为110V的电灯泡串联起来总可以接到220V的电压源上使用。[×]
&nbsp; &nbsp; 解：功率不同的不可以。
.4. 电流相等的两个元件必属串联,电压相等的两个元件必属并联。[×]
.5. 由电源等效变换可知, 如图Ａ所示电路可用图Ｂ电路等效代替，其中则图A中的Ri和RL消耗的功率与图Ｂ中Ri和RL消耗的功率是不变的。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[×]
&nbsp;解：对外等效，对内不等效。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;可举例说明。

.6. 一个不含独立源的电阻性线性二端网络（可以含受控源）总可以等效为一个线性电阻。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[√] &nbsp; &nbsp;
.7. 一个含独立源的电阻性线性二端网络（可以含受控源）总可以等效为一个电压源与一个电阻串联或一个电流源与一个电阻并联。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[√] &nbsp; &nbsp;
.8.已知图示电路中Ａ、Ｂ两点电位相等，则ＡＢ支路中必然电流为零。 &nbsp; &nbsp; [×] &nbsp;
&nbsp; 解：根据KVL有： &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;
&nbsp; &nbsp;
.9. 图示电路中, 既然ＡＢ两点电位相等, 即ＵAB =0,必有IAB =0 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[×]
解：
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.10. 理想电压源不能与任何理想电流源等效。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [√] &nbsp; &nbsp;
二、选择题
(注:在每小题的备选答案中选择适合的答案编号填入该题空白处,多选或不选按选错论)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.1. 图示电路 ＡＢ间的等效电阻为_Ｃ_ &nbsp;

解：二个电阻并联等效成一个电阻，另一电阻断开。
(Ａ) 10.67Ω &nbsp; &nbsp;(Ｂ) 12Ω &nbsp; &nbsp; &nbsp; &nbsp;
(Ｃ) 14Ω &nbsp; &nbsp; &nbsp; (Ｄ) 24Ω
解：二条并联后少一条支路。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

.2. 电路如图所示，Ａ、Ｂ端的等效电阻Ｒ＝_Ａ__ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(Ａ) 4Ω &nbsp; &nbsp;(Ｂ) 5Ω &nbsp; &nbsp; &nbsp;(Ｃ) 10Ω &nbsp; (Ｄ) 20Ω &nbsp; &nbsp; &nbsp;
解：

.3. 电路如图所示，可化简为_Ｃ_。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;解：

&nbsp; &nbsp;
&nbsp; (Ａ) 8Ω电阻 &nbsp; &nbsp; (Ｂ) 13Ω电阻 &nbsp; &nbsp; (Ｃ) 3Ω电阻 &nbsp; &nbsp; (Ｄ) 不能化简 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.4. 如图所示电路中，当电阻Ｒ2增加时电流Ｉ将_Ａ__。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(Ａ) 增加 &nbsp; &nbsp;(Ｂ) 减小 &nbsp; &nbsp;(Ｃ) 不变 &nbsp; &nbsp; &nbsp;
解：

.5. 现有额定值为220V、25W的电灯一只,准备串联一个小灯泡放在另一房间作为它的信号灯,应选择_Ａ_规格的小灯泡? &nbsp;
(Ａ) 6V,0.15A; &nbsp;(Ｂ) 6V,0.1A; (Ｃ) 1.5V,0.5A; (Ｄ) 1.5V,0.3A; (Ｅ) 都不可以
分析思路：； &nbsp; &nbsp;A；舍去（B）；
；；；

额定功率： &nbsp; &nbsp;
实际功率：

（亮度不够）；（亮度不够）。
.6. 图示电路的输出端开路,当电位器滑动触点移动时,输出电压Ｕ2变化的范围为_Ｃ_
(Ａ) 0～4V &nbsp; &nbsp; &nbsp; (Ｂ) 0～5V &nbsp; &nbsp; &nbsp;(Ｃ) (1～4)V &nbsp; &nbsp; (Ｄ)(1～5)V &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;解：
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;

.7. 图示电路中,当开关Ｓ接通时, 电压Ｕ2_Ｃ__,电流Ｉ2_Ｃ_,电压 Ｕ1Ｂ_,电流Ｉ1_Ｂ_。 &nbsp; &nbsp; &nbsp;
(Ａ) 不变 &nbsp; &nbsp; (Ｂ) 增大 &nbsp;
(Ｃ) 减小 &nbsp; &nbsp; (Ｄ) 增大或减小
解： 后，并联值减小；电流增大；
电压增大；电压减小。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.8 . 将２５Ｗ、２２０Ｖ的白炽灯和６０Ｗ、２２０Ｖ的白炽灯串联后接到２２０Ｖ的电源上，比较两灯的亮度是_Ａ_。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (Ａ) ２５Ｗ的白炽灯较亮 &nbsp; &nbsp; (Ｂ) ６０Ｗ的白炽灯较亮 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (Ｃ) 二灯同样亮 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; (Ｄ) 无法确定那个灯亮 &nbsp; &nbsp;
解：串联是通过同一电流，用。２５Ｗ的电阻大。
.9 . 电路如图所示，若电流表Ａ的内阻很小，可忽略不计（即内阻为零），则Ａ表的读数为_Ｃ__。 &nbsp; &nbsp;
(Ａ) ０Ａ &nbsp; &nbsp; (Ｂ) 1/3Ａ &nbsp;
(Ｃ) 1/2Ａ &nbsp; &nbsp;(Ｄ) 2/3Ａ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
解：，,
&nbsp; &nbsp;。
.10. 现有四种直流电压表,为了较准确地测量图示电路的电压,电压表应选用_Ｃ_。
解：
电压表量程应略大于内阻尽可能大。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (Ａ) 量程0～100Ｖ，内阻25 KΩ/Ｖ &nbsp; &nbsp;(Ｂ) 量程0～10Ｖ，内阻20 KΩ/Ｖ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (Ｃ) 量程0～5Ｖ，内阻20 KΩ/Ｖ &nbsp; &nbsp; &nbsp;(Ｄ) 量程0～3Ｖ，内阻1 KΩ/Ｖ &nbsp; &nbsp; &nbsp; &nbsp;
.11. 如图所示电路, 若在独立电流源支路串联接入10Ω电阻,则独立电压源所发出的功率_Ｂ_; 独立电流源发出的功率_Ａ_。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (Ａ) 改变 &nbsp; &nbsp; (Ｂ) 不改变 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
解：
若在独立电流源支路串联接入10Ω电阻,
该支路电压和电流值不变，但独立电流源
上的电压增大。

.12. 图示电路中，就其外特性而言，_Ａ_。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; (Ａ) ｂ、ｃ等效； &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; (Ｂ)ａ、ｄ等效；
&nbsp; (Ｃ) ａ、ｂ、ｃ、ｄ均等效； (Ｄ)ａ、ｂ等效
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.13. 如图所示电路, 增大Ｇ1将导致_Ｃ__。
(Ａ) ＵA增大，ＵB增大 ；
(Ｂ) ＵA减小，ＵB减小； &nbsp; &nbsp;
(Ｃ) ＵA不变，ＵB减小；
(Ｄ) ＵA不变，ＵB增大。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
三、计算题 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
1. 图所示的是直流电动机的一种调速电阻，它由四个固定电阻串联而成。利用几个开关的闭合或断开，可以得到多种电阻值。设4个电阻都是1Ω，试求在下列三种情况下ａ，ｂ两点间的电阻值： &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
（１）Ｋ1和Ｋ5闭合，其他打开；
（２）Ｋ2、Ｋ3和Ｋ5闭合，其他打开； &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
（３）Ｋ1 、Ｋ3和Ｋ4闭合；其他打开。
解：（１）Ｋ1和Ｋ5闭合，其他打开；

（２）Ｋ2、Ｋ3和Ｋ5闭合，其他打开；

（３）Ｋ1 、Ｋ3和Ｋ4闭合；其他打开。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;
2. 求图示电路等效电阻ＲMN.
解：
，
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
3. 试求图示电路的入端电阻ＲAB图中电阻的单位为欧. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; 解：二个电阻并联等效成一个电阻，另一电阻断开。
&nbsp; &nbsp; &nbsp; &nbsp;(1), &nbsp; &nbsp; &nbsp;(2)。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
4. 求图示电路Ａ、Ｂ端的等效电阻ＲAB &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;解：设包含受控源向左的等效电阻为R,

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
5. 在图示电路中, 求当Ｒi =0时的K值。
&nbsp;解：设包含受控源向左的等效电阻为R,
&nbsp;
&nbsp; ，
当Ｒi =0时，必有R=-1Ω，即K=4。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
6. 求图（１）、（２）两电路的输入电阻。
解：（１） &nbsp; &nbsp;
&nbsp; &nbsp;
（２） &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; 7. 图示电路中ＡＢ间短路时电流Ｉ1＝？ &nbsp;
&nbsp; &nbsp; 解：等效电路图如右：

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

8. 试用电源等效变换的方法计算图示电路中1Ω电阻中的电流.
&nbsp; &nbsp; &nbsp;解：等效电路图如下： &nbsp;I=4/9 A。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

9. 试求图示电路中安培表的读数.(Ａ点处不连接) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
解：等效电路图如下：

10. 如图电路中，内阻Ｒ0= 280欧，万用表Ｉ0 的满标值为 0.6 毫安、且有 &nbsp; &nbsp; &nbsp;
Ｒ＝Ｒ1+Ｒ2+Ｒ3=420欧。 如用这个万用表测量直流电压，量程分别为10伏、100伏、和250 伏。试计算Ｒ4、Ｒ5、Ｒ6的阻值。
解：量程分别为10V、100V、和250V时，
万用表Ｉ0 的值不能超满标值 0.6 毫安。

9832Ω；

90 KΩ；同理，。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
11.图示电路中,Ｒ1 &nbsp; 、Ｒ2、Ｒ3 &nbsp;、Ｒ4 的额定值均为6.3Ｖ,0.3Ａ,Ｒ5的额定值为6.3Ｖ,0.45Ａ。为使上述各电阻元件均处于其额定工作状态，问应选配多大阻值的电阻元件ＲX 和ＲY ?
解：
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;，， &nbsp;，
&nbsp; &nbsp; &nbsp;,，
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
12. 应用电源等效变换法求如图所示电路中2Ω支路的电流 . &nbsp; &nbsp;
解： 等效电路图如下：I=35/7=5A。

&nbsp; 13. 电路如图所示，试求独立电压源电流、独立电流源电压以及受控电流源电压。
&nbsp; &nbsp; &nbsp;解：
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; 14. 试求电路中的 &nbsp; &nbsp;
解：

&nbsp; &nbsp; =1.33A, =2.66A, =37.77A。
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; 15. 在图示电路中,用一个电源代替图中的三个电源,并且保持Ｒ1至Ｒ4中的电流和端电压不变。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; 解：等效电路图如下：
&nbsp; &nbsp; &nbsp;

第三章 电阻电路的一般分析
一、是非题 (注:请在每小题后[ &nbsp;]内用&quot;√&quot;表示对,用&quot;×&quot;表示错) &nbsp; &nbsp; &nbsp; &nbsp;
.1. 利用节点ＫＣＬ方程求解某一支路电流时，若改变接在同一节点所有其它已知支路电流的参考方向，将使求得的结果有符号的差别。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; [×] &nbsp;
.2. 列写ＫＶＬ方程时,每次一定要包含一条新支路才能保证方程的独立性。 &nbsp; &nbsp;[√] &nbsp;
.3. 若电路有ｎ个节点，按不同节点列写的ｎ－１个ＫＣＬ方程必然相互独立。 [√] &nbsp;
.4. 如图所示电路中，节点Ａ的方程为：
(1/R1 +1/ R2 +1/ R3)Ｕ =IS+ＵS/Ｒ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[×]
&nbsp;解：关键点：先等效，后列方程。
图A的等效电路如图B： &nbsp; &nbsp; &nbsp;
&nbsp;节点Ａ的方程应为： &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

.5. 在如图所示电路中, 有 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; [√] &nbsp;
&nbsp; 解：图A的等效电路如图B：
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

.6. 如图所示电路,节点方程为: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
； ； &nbsp;. &nbsp; &nbsp; &nbsp;[×]
&nbsp;解：图A的等效电路如图B：

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

.7. 如图所示电路中,有四个独立回路。各回路电流的取向如图示, 则可解得各回路 &nbsp; &nbsp; &nbsp;
电流为: Ｉ1＝１Ａ；Ｉ2＝２Ａ； Ｉ3＝３Ａ；Ｉ4＝４Ａ。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;[×]
&nbsp;解：
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp;
&nbsp; &nbsp; &nbsp;

二、选择题 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(注:在每小题的备选答案中选择适合的答案编号填入该题空白处,多选或不选按选错论) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.1. 对如图所示电路，下列各式求支路电流正确的是 Ｃ_。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
(Ａ) ; &nbsp;(Ｂ) &nbsp; &nbsp; &nbsp; &nbsp;(Ｃ) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.2. 若网络有b条支路、n个节点,其独立ＫＣＬ方程有_Ｃ_个,独立ＫＶＬ方程有_Ｄ__个,共计为_Ａ_个方程。若用支路电流法，总计应列_Ａ_个方程;若用支路电压法,总计应列_Ａ_个方程。 &nbsp;

（Ａ）ｂ &nbsp;（Ｂ）２ｂ &nbsp;（Ｃ）ｎ－１ （Ｄ）ｂ－ｎ＋１ &nbsp;
.3. 分析不含受控源的正电阻网络时，得到下列的节点导纳矩阵Ｙn，其中肯定错误的为_ B 、C 、_ D 、E _。 &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;(A) (B) &nbsp; (C) &nbsp; (D) &nbsp; &nbsp;(E) &nbsp;解：自导为正，值大互导；互导为负，其值相等。
.4. 列写节点方程时,图示部分电路中Ｂ点的自导为_Ｆ_Ｓ, ＢＣ间的互导为Ｄ_Ｓ,Ｂ点的注入电流为_Ｂ_A 。
(A) 2 &nbsp; &nbsp; (Ｂ) -14 &nbsp; &nbsp;(Ｃ) 3 &nbsp; &nbsp;(Ｄ) -3 &nbsp; &nbsp; (Ｅ) -10 &nbsp; &nbsp; &nbsp;(Ｆ) 4 &nbsp; &nbsp; &nbsp;
&nbsp;解：图A的等效电路如图B：
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.5. 图示电路中各节点的电位分别为 Ｖ1、Ｖ2 、Ｖ3,则节点②的ＫＣＬ方程: &nbsp; &nbsp; &nbsp;
( &nbsp;) + 0.5Ｉ+ 2 = 0 &nbsp;,括号中应为_Ｃ__.
(Ａ) Ｖ1/3 &nbsp; (Ｂ) (Ｖ2-Ｖ1)/3 &nbsp;
(Ｃ) 3(Ｖ2-Ｖ1) &nbsp;(Ｄ) 3(Ｖ1-Ｖ2) &nbsp;
&nbsp; 解：
&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
.6. 电路如图所示, Ｉ＝_Ｄ_。
&nbsp; (Ａ) 25ｍＡ &nbsp; &nbsp; (Ｂ) 27.5ｍＡ &nbsp; &nbsp;
&nbsp; (Ｃ) 32.5ｍＡ &nbsp; (Ｄ)</p>