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大小:1.76 MB
页数:34页
时间:2020-09-22
《恒定电流实验基础ppt课件.ppt》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.温故自查1.灵敏电流表(1)三个主要参数①内阻Rg②满偏电流Ig③满偏电压Ug(2)三个参数间的关系:由欧姆定律知Ug=IgRg2.电表的改装(1)电压表改装时所加电阻与电流表G串联起来.(2)电流表改装时所加电阻与电流表G并联起来.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientPr
2、ofile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.即电压扩大量程倍数为n时,需要串联的分压电阻R=(n-1)Rg.电压表的内阻RV=Rg+R,即RV等于Rg与R串联时的总电阻.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0
3、.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.命题规律根据电表改装原理确定电压表、电流表的量程,或改装成电流表、电压表需并联、串联多大电阻.[考例1]如果两个电流表的满偏电流均为Ig=3mA,内阻Rg=100Ω,欲将其改装成量程分别为3V和15V的电压表,则:(1)分别串联的电阻R1和R2为多大?(2)将改装后的电压表串联后
4、测电路中电阻的电压时,指针的偏角θ1和θ2有何关系,示数U1和U2有何关系?Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.(2)将两只电压表串联后测电压,即如图所示连接,因流过表头的电流相同,
5、故偏角θ1=θ2,而电压表内阻RV1、RV2有关系RV1/RV2=1/5,故电压表示数之比为U1:U2=1:5.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.[答案](1)900 4900 (2)θ1=θ21:5[总结评述]改装后电表中表头的满偏电流、电压并不改变,只要将灵敏电流表的表盘按扩大量程后的倍数加以改换,即可从表盘上直接读出电路中的总电压或电路的总电流的数值.Evaluationo
6、nly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.2.两种测量电阻的电路:(如图所示)内接法外接法Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfi
7、le5.2.0.0.Copyright2004-2011AsposePtyLtd.3.两种控制电路:(如图所示)Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.考点精析1.伏安法测电阻的电路选择(1)阻值比较法:先将待测电阻的估计值与电压表、电流表的内阻进行比较,若Rx较小.宜采用电流表外接法;若Rx较大,宜采用电流表内接法.(2)临界值计算法:Evaluationonly.Createdwi
8、thAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLt
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