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电阻

电(dian)(dian)(dian)阻(zu)是描(miao)述导体(ti)导电(dian)(dian)(dian)性能(neng)的(de)(de)(de)(de)(de)物理量(liang)，用R表示。电(dian)(dian)(dian)阻(zu)由导体(ti)两端的(de)(de)(de)(de)(de)电(dian)(dian)(dian)压(ya)U与通过(guo)导体(ti)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)流(liu)I的(de)(de)(de)(de)(de)比值来(lai)(lai)定义，即R=U/I。所以(yi)，当导体(ti)两端的(de)(de)(de)(de)(de)电(dian)(dian)(dian)压(ya)一(yi)定时，电(dian)(dian)(dian)阻(zu)愈(yu)大(da)，通过(guo)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)流(liu)就愈(yu)小; 反之，电(dian)(dian)(dian)阻(zu)愈(yu)小，通过(guo)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)流(liu)就愈(yu)大(da)。因此(ci)，电(dian)(dian)(dian)阻(zu)的(de)(de)(de)(de)(de)大(da)小可以(yi)用来(lai)(lai)衡(heng)量(liang)导体(ti)对电(dian)(dian)(dian)流(liu)阻(zu)碍(ai)作用的(de)(de)(de)(de)(de)强(qiang)弱，即导电(dian)(dian)(dian)性能(neng)的(de)(de)(de)(de)(de)好坏。电(dian)(dian)(dian)阻(zu)的(de)(de)(de)(de)(de)量(liang)值与导体(ti)的(de)(de)(de)(de)(de)材料、形(xing)状、体(ti)积以(yi)及(ji)周围环境(jing)等因素(su)有关(guan)。

不同导(dao)(dao)体的(de)电(dian)(dian)(dian)(dian)阻(zu)(zu)按其性(xing)(xing)质的(de)不同还(hai)可(ke)分为(wei)两种类(lei)型。一(yi)类(lei)称(cheng)(cheng)(cheng)为(wei)线性(xing)(xing)电(dian)(dian)(dian)(dian)阻(zu)(zu)或欧(ou)姆电(dian)(dian)(dian)(dian)阻(zu)(zu)，满足欧(ou)姆定(ding)(ding)律; 另(ling)一(yi)类(lei)称(cheng)(cheng)(cheng)为(wei)非(fei)线性(xing)(xing)电(dian)(dian)(dian)(dian)阻(zu)(zu)，不满足欧(ou)姆定(ding)(ding)律。电(dian)(dian)(dian)(dian)阻(zu)(zu)的(de)倒(dao)数1/R称(cheng)(cheng)(cheng)为(wei)电(dian)(dian)(dian)(dian)导(dao)(dao)，也是(shi)描(miao)述(shu)导(dao)(dao)体导(dao)(dao)电(dian)(dian)(dian)(dian)性(xing)(xing)能的(de)物(wu)理量，用(yong)G表(biao)示。电(dian)(dian)(dian)(dian)阻(zu)(zu)的(de)单(dan)(dan)位(wei)(wei)在国际单(dan)(dan)位(wei)(wei)制(zhi)中是(shi)欧(ou)姆(Ω)，简称(cheng)(cheng)(cheng)欧(ou)。而电(dian)(dian)(dian)(dian)导(dao)(dao)的(de)国际单(dan)(dan)位(wei)(wei)制(zhi)(SI)单(dan)(dan)位(wei)(wei)是(shi)西门子(S)，简称(cheng)(cheng)(cheng)西。电(dian)(dian)(dian)(dian)阻(zu)(zu)还(hai)常(chang)用(yong)kΩ和MΩ作单(dan)(dan)位(wei)(wei)，它们之(zhi)间的(de)关系是(shi)：1MΩ=1000kΩ=1000000Ω

电(dian)(dian)阻(zu)率(lv)描(miao)(miao)述(shu)导(dao)(dao)体导(dao)(dao)电(dian)(dian)性(xing)能(neng)的(de)参(can)数。对(dui)于由某种材料制(zhi)成(cheng)的(de)柱形均匀导(dao)(dao)体，其(qi)(qi)电(dian)(dian)阻(zu)R与(yu)长度(du)L成(cheng)正比，与(yu)横截面(mian)积S成(cheng)反(fan)比，即： 式(shi)中ρ为(wei)比例(li)系(xi)(xi)数，由导(dao)(dao)体的(de)材料和周围温(wen)度(du)所决(jue)定，称为(wei)电(dian)(dian)阻(zu)率(lv)。它(ta)的(de)国际单(dan)位制(zhi)(SI)是欧姆·米(mi) (Ω·m)。常温(wen)下(xia)一般金属(shu)的(de)电(dian)(dian)阻(zu)率(lv)与(yu)温(wen)度(du)的(de)关系(xi)(xi)为(wei)：ρ=ρ0(1+αt)式(shi)中ρ0为(wei)0℃时(shi)的(de)电(dian)(dian)阻(zu)率(lv); α为(wei)电(dian)(dian)阻(zu)的(de)温(wen)度(du)系(xi)(xi)数; 温(wen)度(du)t的(de)单(dan)位为(wei)摄氏温(wen)度(du)。半(ban)导(dao)(dao)体和绝缘(yuan)体的(de)电(dian)(dian)阻(zu)率(lv)与(yu)金属(shu)不同，它(ta)们与(yu)温(wen)度(du)之间不是按线性(xing)规(gui)律(lv)变化的(de)。当温(wen)度(du)升高(gao)时(shi)，它(ta)们的(de)电(dian)(dian)阻(zu)率(lv)会急(ji)剧地减(jian)小。呈现出非线性(xing)变化的(de)性(xing)质。电(dian)(dian)阻(zu)率(lv)的(de)倒数1/ρ称为(wei)电(dian)(dian)导(dao)(dao)率(lv)，用σ表示。它(ta)也是描(miao)(miao)述(shu)导(dao)(dao)体导(dao)(dao)电(dian)(dian)性(xing)能(neng)的(de)参(can)数 ，其(qi)(qi)国际单(dan)位制(zhi)(SI)是西门(men)子/米(mi) (S/m)。

电阻的工作原理

电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)工作原(yuan)理(li)在物(wu)(wu)理(li)学中，用电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)来表(biao)示导(dao)体(ti)(ti)对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)阻(zu)(zu)(zu)碍(ai)作用的(de)大(da)小。导(dao)体(ti)(ti)的(de)电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)越(yue)大(da)，表(biao)示导(dao)体(ti)(ti)对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)阻(zu)(zu)(zu)碍(ai)作用越(yue)大(da)。不同的(de)导(dao)体(ti)(ti)，电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)一般不同，电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)是(shi)导(dao)体(ti)(ti)本身的(de)一种特(te)性。电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)元(yuan)件(jian)(jian)是(shi)对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)呈现(xian)阻(zu)(zu)(zu)碍(ai)作用的(de)耗(hao)能元(yuan)件(jian)(jian)。因为(wei)物(wu)(wu)质对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)产(chan)(chan)生的(de)阻(zu)(zu)(zu)碍(ai)作用，所(suo)以(yi)称其(qi)该(gai)作用下的(de)电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)物(wu)(wu)质。电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)将会导(dao)致电(dian)(dian)(dian)(dian)(dian)(dian)子流(liu)(liu)通量(liang)(liang)(liang)的(de)变化(hua)，电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)越(yue)小，电(dian)(dian)(dian)(dian)(dian)(dian)子流(liu)(liu)通量(liang)(liang)(liang)越(yue)大(da)，反之(zhi)亦(yi)然。电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)元(yuan)件(jian)(jian)的(de)电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)值大(da)小一般与(yu)温(wen)度(du)，材料，长度(du)，还有横截面积有关(guan)，衡量(liang)(liang)(liang)电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)受温(wen)度(du)影响(xiang)大(da)小的(de)物(wu)(wu)理(li)量(liang)(liang)(liang)是(shi)温(wen)度(du)系(xi)数(shu)，其(qi)定义为(wei)温(wen)度(du)每升高1℃时电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)值发生变化(hua)的(de)百分数(shu)。电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)主(zhu)要物(wu)(wu)理(li)特(te)征(zheng)是(shi)变电(dian)(dian)(dian)(dian)(dian)(dian)能为(wei)热能，也可说(shuo)它是(shi)一个耗(hao)能元(yuan)件(jian)(jian)，电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)经过它就产(chan)(chan)生内能。电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)在电(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中通常(chang)起分压、分流(liu)(liu)的(de)作用。对(dui)信(xin)号来说(shuo)，交流(liu)(liu)与(yu)直流(liu)(liu)信(xin)号都可以(yi)通过电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)。

热敏电阻(zu)：是一种(zhong)对温度极为敏感的电阻(zu)器(qi)。

光敏电(dian)(dian)阻：分为正温(wen)度(du)系(xi)(xi)数(shu)(shu)和负(fu)温(wen)度(du)系(xi)(xi)数(shu)(shu)电(dian)(dian)阻器。选(xuan)用时不仅要(yao)(yao)注(zhu)(zhu)意(yi)其额定功率(lv)、最(zui)大(da)工作电(dian)(dian)压、标称(cheng)阻值(zhi)，更要(yao)(yao)注(zhu)(zhu)意(yi)最(zui)高工作温(wen)度(du)和电(dian)(dian)阻温(wen)度(du)系(xi)(xi)数(shu)(shu)等(deng)参数(shu)(shu)，并注(zhu)(zhu)意(yi)阻值(zhi)变化方向(xiang)。硫(liu)化镉(ge)等(deng)材质，阻值(zhi)随着光线(xian)的(de)强弱而(er)发生变化的(de)电(dian)(dian)阻器。分为可见光光敏电(dian)(dian)阻、红(hong)外(wai)光光敏电(dian)(dian)阻、紫外(wai)光光敏电(dian)(dian)阻。选(xuan)用时先确定电(dian)(dian)路的(de)光谱特性。

电阻的作用
电阻耦合作用

在低(di)频信(xin)(xin)号的传递(di)与放大过程中，为防(fang)止前后两级(ji)电路(lu)的静态(tai)工(gong)作(zuo)点相互影响，常采用电容(rong)藕合．为了防(fang)止信(xin)(xin)号中韵(yun)低(di)频分量损失过大，一般总采用容(rong)量较大的电解(jie)电容(rong)。

电感

电(dian)(dian)(dian)(dian)(dian)(dian)感是(shi)衡量(liang)线(xian)(xian)圈产(chan)生电(dian)(dian)(dian)(dian)(dian)(dian)磁感应(ying)能力(li)的(de)(de)(de)物理量(liang)。给一个线(xian)(xian)圈通(tong)(tong)(tong)入电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，线(xian)(xian)圈周围就会产(chan)生磁场(chang)，线(xian)(xian)圈就有(you)磁通(tong)(tong)(tong)量(liang)通(tong)(tong)(tong)过(guo)。通(tong)(tong)(tong)入线(xian)(xian)圈的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)源越大(da)，磁场(chang)就越强，通(tong)(tong)(tong)过(guo)线(xian)(xian)圈的(de)(de)(de)磁通(tong)(tong)(tong)量(liang)就越大(da)。实(shi)验(yan)证明，通(tong)(tong)(tong)过(guo)线(xian)(xian)圈的(de)(de)(de)磁通(tong)(tong)(tong)量(liang)和通(tong)(tong)(tong)入的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)是(shi)成正比(bi)的(de)(de)(de)，它们(men)的(de)(de)(de)比(bi)值(zhi)叫做自感系数，也(ye)叫做电(dian)(dian)(dian)(dian)(dian)(dian)感。 电(dian)(dian)(dian)(dian)(dian)(dian)感的(de)(de)(de)特(te)(te)性(xing)与电(dian)(dian)(dian)(dian)(dian)(dian)容的(de)(de)(de)特(te)(te)性(xing)正好相反(fan)，它具有(you)阻(zu)(zu)止交流(liu)电(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)(tong)过(guo)而让直流(liu)电(dian)(dian)(dian)(dian)(dian)(dian)顺(shun)利(li)通(tong)(tong)(tong)过(guo)的(de)(de)(de)特(te)(te)性(xing)。电(dian)(dian)(dian)(dian)(dian)(dian)感的(de)(de)(de)特(te)(te)性(xing)是(shi)通(tong)(tong)(tong)直流(liu)、阻(zu)(zu)交流(liu)，频率越高，线(xian)(xian)圈阻(zu)(zu)抗越大(da)。电(dian)(dian)(dian)(dian)(dian)(dian)感器在电(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中经常和电(dian)(dian)(dian)(dian)(dian)(dian)容一起工(gong)作，构成LC滤(lv)波器、LC振荡(dang)器等。另外，人们(men)还(hai)利(li)用电(dian)(dian)(dian)(dian)(dian)(dian)感的(de)(de)(de)特(te)(te)性(xing)，制(zhi)造了阻(zu)(zu)流(liu)圈、变压器、继电(dian)(dian)(dian)(dian)(dian)(dian)器等。

采集非电量参量

我们(men)知道，电阻值与温度(du)之间存(cun)在一(yi)定(ding)的关系(xi)。看(kan)下式：

在这(zhei)里，电(dian)(dian)(dian)阻值R与温(wen)度(du)T之间(jian)存在函(han)数关系(xi)。于是，我们(men)就可以用电(dian)(dian)(dian)阻来(lai)采集温(wen)度(du)。采集温(wen)度(du)的(de)(de)电(dian)(dian)(dian)阻有两种(zhong)，一种(zhong)叫(jiao)做正温(wen)度(du)系(xi)数的(de)(de)热(re)敏(min)电(dian)(dian)(dian)阻，另一种(zhong)叫(jiao)做负温(wen)度(du)系(xi)数的(de)(de)热(re)敏(min)电(dian)(dian)(dian)阻。这(zhei)两种(zhong)热(re)敏(min)电(dian)(dian)(dian)阻的(de)(de)用途都很(hen)广泛。电(dian)(dian)(dian)阻还可以用来(lai)采集其(qi)它(ta)物(wu)理量，例(li)如压(ya)敏(min)电(dian)(dian)(dian)阻和光敏(min)电(dian)(dian)(dian)阻等等。

可作为元件的身份证

此图(tu)的(de)纵坐标(biao)是电流(liu)I，横(heng)坐标(biao)是电压U。此图(tu)又(you)叫做电流(liu)-电压特(te)性曲(qu)线图(tu)，更(geng)多的(de)时(shi)候(hou)简称为(wei)伏安特(te)性曲(qu)线。根据欧姆(mu)定律，我们有(you)：

这(zhei)里的(de)(de)(de)R称(cheng)为(wei)(wei)(wei)动(dong)态电(dian)(dian)阻(zu)(zu)，它其实就是(shi)曲(qu)(qu)(qu)(qu)线(xian)(xian)(xian)斜(xie)率(lv)的(de)(de)(de)倒数。当R大于零时(shi)，被(bei)称(cheng)为(wei)(wei)(wei)正(zheng)阻(zu)(zu)特性，反之(zhi)，当动(dong)态电(dian)(dian)阻(zu)(zu)R小(xiao)于零时(shi)，被(bei)称(cheng)为(wei)(wei)(wei)负阻(zu)(zu)特性。???对于蓝色的(de)(de)(de)曲(qu)(qu)(qu)(qu)线(xian)(xian)(xian)，我们(men)(men)看出它是(shi)一条经过(guo)原点的(de)(de)(de)直线(xian)(xian)(xian)，它的(de)(de)(de)动(dong)态电(dian)(dian)阻(zu)(zu)阻(zu)(zu)值(zhi)不随(sui)着(zhe)电(dian)(dian)压和电(dian)(dian)流(liu)的(de)(de)(de)变化(hua)而变化(hua)，满足这(zhei)种伏(fu)安特性曲(qu)(qu)(qu)(qu)线(xian)(xian)(xian)的(de)(de)(de)元(yuan)(yuan)件(jian)被(bei)称(cheng)为(wei)(wei)(wei)线(xian)(xian)(xian)性元(yuan)(yuan)件(jian);反之(zhi)，对于红色的(de)(de)(de)曲(qu)(qu)(qu)(qu)线(xian)(xian)(xian)，我们(men)(men)看出它是(shi)一条曲(qu)(qu)(qu)(qu)线(xian)(xian)(xian)，它的(de)(de)(de)动(dong)态电(dian)(dian)阻(zu)(zu)阻(zu)(zu)值(zhi)随(sui)着(zhe)电(dian)(dian)压和电(dian)(dian)流(liu)的(de)(de)(de)变化(hua)而变化(hua)。满足这(zhei)种伏(fu)安特性曲(qu)(qu)(qu)(qu)线(xian)(xian)(xian)的(de)(de)(de)元(yuan)(yuan)件(jian)被(bei)称(cheng)为(wei)(wei)(wei)非线(xian)(xian)(xian)性元(yuan)(yuan)件(jian)。

电阻单位表示及计算公式

导体的电(dian)阻通(tong)常用字母(mu)R表示，电(dian)阻的单位(wei)是(shi)欧(ou)姆（ohm），简称(cheng)欧(ou)，符号是(shi)Ω（希腊字母(mu)，读作Omega)，1Ω=1V/A。比较大(da)的单位(wei)有千(qian)(qian)欧(ou)（kΩ）、兆(zhao)(zhao)欧(ou)（MΩ）（兆(zhao)(zhao)=百万(wan)，即100万(wan)）。KΩ（千(qian)(qian)欧(ou)）， MΩ（兆(zhao)(zhao)欧(ou)），他们的换算关系是(shi)：两个电(dian)阻并(bing)联式也(ye)可(ke)表示为(wei)：1TΩ=1000GΩ；1GΩ=1000MΩ；1MΩ=1000KΩ；1KΩ=1000Ω（也(ye)就是(shi)一千(qian)(qian)进率）。

计算公(gong)式为：

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