文档介绍：伏安法测电阻 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. ??欧姆定律给了我们测量电阻的一种方?法,由 R=…可知,用电压表测出电?阻两端的电压,用电流表测出通过电阻的电流,就可求出待测电阻. Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. ?外接法内接法 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. ??(1) 电流表外接法:由于电压表的分流导致电流的测量值偏大,由 R=可知, R 测<R 真, R越小,电压表分流越小,误差越小,因此这种接法适合测小电阻, (2) 电流表内接法:由于电流表的分压, R=得R 测>R 真, R越大,电流表的分压越小,. Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. ?、外接的常用方法?(1) 直接比较法:适用于 R x、R A、R V的大小大致可以估计,当 R x?R A时,采用内接法,当 R x?R V时,采用外接法,即大电阻用内接法, 小电阻用外接法,可记忆为“大内小外”. (2) 公式计算法: 当时,用内接法; 当时,用外接法; Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. ?(3) 试触法:适用于 R x、R V、R A的阻值关系都不能确定的情况,如图所示,把电压表的接线端分别接 b、c两点,观察两电表的示数变化,若电流表的示数变化明显,说明电压表的分流对电路影响大,应选用内接法,若电压表的示数有明显变化,说明电流表的分压作用对电路影响大,所以应选外接法. Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 例题:伏安法测电阻的接法有如图中甲、乙两种,下列说法正确的是()